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It's something I've seen as trial and error, but to make it a little more technical I haven't seen a route for this process. Does anyone have ideas for this route?
I'm talking about the case of rotational reometers.
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Dear Juan Fernando Hernandez, what is this unseen before finding? You forgot to mention that. My Regards
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I am working with gelatin hydrogels and want to measure the amount of amino acids, which were substituted.
I thought about doing a "quick and simple" ninhydrin assay and figured out it does not work. There are plenty protocols available online. Some are adding hydrindantin and some do not. How important is hydrindantin for the reaction of the ninhydrin assay?
I thought that hydrindantin would appear during the ninhydrin reaction anyway so there is no need to add it. Unfortunately, none of my assays worked. I get a very slight reaction with 0.5 mg/mL gelatin concentration and 3.5 mg/mL ninhydrin solution in ddH2O; mix in sample:ninhydrin-ratio 1:1; 80 degree waterbath and 15 min reaction time. I also tried other assays and this was the best reaction I could get. Unfortunately, the absorbance of the substituted gelatin was higher than the raw gelatin which is impossible since the amino acids are blocked by substitution, so less reaction sides for ninhydrin.
Would you suggest buying hydrindantin (which is pretty expensive) or would you recommend another ninhydrin assay?
My stock solutions are fine; I already tested it with TNBS.
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It is not important to add hydrindantin for the reaction of the ninhydrin assay.
  • You can add some reducing agent in the reaction mixture (such as NaBH4) which will help to make the complex Ruhemann's purple colour.
  • Make sure that when you are preparing ninhydrin solution its well dissolve in EtOH and use saturated solution.
  • In some cases it takes longer time, so, you can do the reaction for 30-35 min at 80 degC and then it will nicely works.
Thanks
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I am doing surface modification of polymer films using plasma in order to improve anti bacterial property.
Thickness of polymer film is 60 micron to 1 mm for different polymers.
I want to test it against E-Coli species.
What are the testing methods suitable to such substrates?
This work is in the direction of developing antimicrobial catheter surfaces.
Thank you in advance.
With kind regards,
Purvi
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As mentioned by Mr Damian, you must be sure that you can sterilise the sample without disrupting the plasma treatment. This is usually done through UV B exposure in a cell culture hood. You will need to find a lab which is capable of performing microbial culture. Some people use ISO 22196:2011 although this will only work on very smooth samples. Another option is to use a confocal microscope and either GFP tagged bacteria or a dye such as LIVE/DEAD to quantify bacterial attachment to the surface. We did some similar analysis here and I would recommend reading Andrew Hooks paper on '
Combinatorial discovery of polymers resistant to bacterial attachment. It is important to consider how you expect your polymer to kill bacteria, or just prevent the attachment.
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I adsorbed my saliva on a PDMS surface. Now I want to recycle the PDMS but I can't rub this surface -- it is too fragile! Do you have any method to completely remove the salivary proteins on a PDMS surface? Any organic solution recommended? Thank you!
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Thank you Saeed Samani for your suggestion :)
I will try the methods you provided and see if they work perfectly in my PDMS system.
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I have an important presentation next week and I would thankful if you could help me.
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We got this question according to differences in structure of cortical and spongy bone.
And is there any differences between bone material before and after remodeling?
How long does remodeling take?
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Trabecular bone and cortical bone have different bone remodeling levels, and the underlying mechanisms are not fully understood. In the present study, the expression of Wnt/β-catenin signaling and its downstream molecules along with bone mass in trabecular and cortical bone were compared in wild-type mice, constitutive activation of β-catenin (CA-β-catenin) mice and β-catenin deletion mice. It was found that the expression level of most of the examined genes such as Wnt3a, β-catenin, osteocalcin and RANKL/OPG ratio were significantly higher in trabecular bone than in cortical bone in wild-type mice. CA-β-catenin resulted in up-regulated expression of the above-mentioned genes except for RANKL/OPG ratio, which were down-regulated. Also, CA-β-catenin led to increased number of osteoblasts, decreased number of osteoclasts and increased bone mass in both the trabecular bone and cortical bone compared with wild-type mice; however, the extent of changes was much greater in the trabecular bone than in the cortical bone. By contrast, null β-catenin led to down-regulated expression of the above-mentioned genes except for RANKL/OPG ratio. Furthermore, β-catenin deletion led to decreased number of osteoblasts, increased number of osteoclasts and decreased bone mass when compared with wild-type mice. Again, the extent of these changes was more significant in trabecular bone than cortical bone. Taken together, we found that the expression level of Wnt/β-catenin signaling and bone remodeling-related molecules were different in cortical bone and trabecular bone, and the trabecular bone was more readily affected by changes in the Wnt/β-catenin signaling pathway. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:812-819, 2017.
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We have an assay that measures the formation of p-nitroalanine (Extinction coefficient 9920cm-1M-1) and have carried out the assay in Corning flat bottom 96 well plates with a final volume of 200ul. Following Corning's data (http://csmedia2.corning.com/LifeSciences/Media/equipment_compatibility/MD_Microplate_Dimension_Sheets.htm) that the wells hold 360ul and the depth is 10.67mm we assume L is 0.593 cm. Is there a more accurate way to determine this as the meniscus is an issue in 96 well plates?
We have a standard curve and can calculate the [p-NA] from this but it was the pathlength correction issue we were interested in.
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You can determine pathlength empirically: fill 3-4 replicate wells with the same volume of water as your samples. Measure absorbance at 900 nm (A900) and 977 nm (A977). Calculate means for A900 and A977 and determine your pathlength (cm) as (A977-A900)/0.18.
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Is this done before?what are the side effects? (Disadvantages)
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And what happens if we accidentally introduce the new DNA into a region that is able to mobilize? Or if the introduced DNA causes mobilization. then what? Perhaps we inadvertently introduce DNA into a gene promoter region, inadvertently because we do not know all the gene promoter regions, and we alter gene expression in the developing embryo. Sure, some people will want their children to have a certain color of eye, but the risks are too great. Even with the moral issues, which are huge, the technicial uncertainty of the workings of the human genome make this a very complex problem. In my opinion, we do not know enough about the human genome and gene expression to make this an option.
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I am developing a hydrogel system combining 2 polymers. They are miscible with each other and form a very clear solution. However, upon photopolymerisation, the resulting hydrogels are very cloudy. If I air dry the hydrogels, they become clear but become cloudy again after rehydration (just with water). What can be the reason behind it? How can I deal with this?
Thanks a lot in advance.
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Thanks all for your answers. I found polymer conc. had an effect on phase separation
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drug eluting stents are the second generation of stent that deliver the drugs on the vesseles wall. many research has been done on these stents.
I want to know are these stents available for all of countries or not.
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In our country, the price of stents also dropped significantly. On the one hand, thanks to the centralized procurement of the state. On the other hand, thanks to the launch of new companies on the market.
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It looks that the material of a child's bone is different from an old man's bone.
How does it change? And what does it depend on?
What is its mechanism?
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Bone is a composite material formed by an inorganic rigid and fragile component (hydroxyapatite) and a resilient organic matrix of collagen.
The softer organic component is higher in children and, therefore, its is less rigid and prone to creep under loading (the organic component, where the bone growth mechanisms reside, is characterized by a viscoelastic behavior). This is an advantage for the younger bones (toddlers boys) since they do not easily break under shock load, however they easily deform under continuous loadings. At increasing ages, the amount of collagen reduces increasing the bone rigidity and strength but becoming more fragile and prone to fracture.
In youngers bones its behavior should be considered viscoelastic and resilient, while in older people it should be considered elastic and fragile.
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we khnow that befor a product marketed,needed FDA approvals,I want to know how many polymers have a this approves.
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Adding to Amin, PBS and PBSA are bioplastics that are listed in U.S. FCN (approved by FDA).  You can also find it in above link.
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as we know both of them are mechanism of blood vessel formation,but i want to know what is diffrence between these mechanism.
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Hi Tahura
in a simple term
vasculogenesis:  formation of the new vascular network when there are no pre-existing vessels.
angiogenesis:  formation of the new vascular network by sprouting and splitting from pre-existing vessels.
Please see the following articles for more info:
Cancer Treat Res. 2004;117:3-32.
Vasculogenesis and angiogenesis.
The Cell Cycle in the Central Nervous System pp 31-41
Vasculogenesis and Angiogenesis
I hope it will help
Amin
I hope it will help
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I need to add a custom material properties in material library for FEA. The properties required should be the mass density, young modulus, poisson's ratio and yield strength for both the cortical bone and cancellous bone. Is there any recorded properties for the bone with human age around 40-60 and early 20s? TQ
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"Mechanical Testing of Bone and the Bone-Implant Interface"
Yuehuei H. An, Robert A. Draughn
you can find you requirnents
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I'm on a low budget, which is why i opted for urea because it is supposed to reduce the hydrophobicity of the fibroin protein, but so far I've achieved nothing with it.I In my last attempt, I dipped the two cocoon silks in 9.3 M of urea for 4 hours at a temperature of 60 degrees celsius. Any suggestions? Thanks in advance. 
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Hi,
Its an interesting question that I like to discuss it further: before, I like to ask
Could you find a way to dissolve in urea? or not yet?
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My solution is Polycapralactone blended in some single and binary solvents. I would like to measure the surface tension with a volume of 1-5ml.
Wilhelmy plate method requires 20-40ml and I cannot use the pendant drop method since my solvents are volatile. Therefore, time is also a factor. But the more important criteria is the volume of solution required.
Thank you in advance!
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I would suggest this book chapter. it has some interesting yet simple methods
Yuan, Yuehua, and T. Randall Lee. "Contact angle and wetting properties." Surface science techniques. Springer Berlin Heidelberg, 2013. 3-34.
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Most of the naturally available biodegradable materials such as agarose, chitin, chitosan, collagen, hyaluronan, gelatin etc. have already been explored. What else can I try? How about pectin?
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Dear Saha, 
Skin regeneration requires scaffolds of well defined characteristics, in terms of tensile properties, micro-structure and morphology, surface modifications by specific cell adhesive proteins, etc. The choice of the polymer is not enough to let you conclude that it works or not, unless you explore the impact of the aforementioned characteristics which I listed above. The micro-fabrication of your scaffold impact the biological performance, the internal structure of the scaffold counts. How did you produce your scaffolds? thin films; non woven mesh, oriented porous scaffolds, filaments deposition? did you explored the impact of these parameters using ONE promising polymer, as gelatin or collagen for example?
I think that the development of scaffold for skin regeneration goes beyond the simple screening of polymers.
Bests,
Irini Gerges, PhD 
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I will be trying to assess the biocompatibility of cellulose acetate - polylactic acid nanofibers in wound healing applications by subjecting it to hemolysis, cytotoxicity and proliferation assays. Is there a commercial wound dressing that actually interacts with the wound or degrades as the wound heals? I plan on using such, if it exists, as a control.
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Oasis, Promogran/Prisma, Endoderm.  These are all collagen matrix dressings and are much less expensive than the before mentioned suggestions.
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This is for a tissue engineering project on 3D printing of biomaterial scaffolds as a substitute for bone grafting. 
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Hi Jethro,
3D printing scaffold is in relation to what technique you want use  (cell encapsulation, printing system, etc), hence you should be more accurate in regard, anyway this paper is a good starting point: http://www.nature.com/nbt/journal/v34/n3/full/nbt.3413.html
Good luck
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This is for testing if a biomaterial scaffold is capable of angiogenesis.
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Dear Jethro. The attached paper shows and compares different ways of quantifying angiogenesis in scaffolds and may be of some help. Best Regards. Deon
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Along the margins in the definition of “bioactivity”, the term “bioactivity” was coined to refer to those materials that can develop a direct, adherent, and strong bonding with the bone tissue. To evaluate the bioactivity of the materials, it has been proposed that materials that form an apatite on their surfaces in the SBF also can form the apatite in a living body and can bond to bone through the apatite layer. In other words, the apatite-forming ability in the SBF is a measure of in vivo bioactivity.
A cellular SBF was used for in vitro experiments. The SBF solution was prepared according to the procedure described by Kokubo and Takadama. Ion concentrations of SBF are similar to those in human blood plasma .
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How to measure bone-like apatite rate? – by weight changing of your samples during the fixed periods of time (e.g., the initial weight was 1 g, after 24 hours of soaking it became 1.1 g, therefore, the rate was 0.1 g/24 hours). Similar calculations can be done by following the concentration decreasing of the major ions.
or From SEM of soaked sample how to measure the rate of apatite formation? – by thickness increasing of the deposits during the fixed periods of time. To get the best results, a combination of all 3 techniques (weight changing, concentration decreasing and thickness increasing) should be used.
Is there any formula or software? – no it is not.
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I am looking for a hydrogel material with the following properties:
- Non-degradable
- Transparent
- Rather soft
- Biocompatible
- Encapsulate live cells, but doesn't need to promote cell adhesion
There seem to be endless choices of hydrogels, but when it comes to non-degradable materials... Anything from personal experience to where to find an overview of potential canditates would be very helpful :)
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Hello Sonja ,
20PEG-8VS seems like a good choice.
Check this paper out.
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What about the thermal capacity of Hydrogels in comparison to water? Is there a possibility to enlarge the specific thermal capacity of water by an e.g. hydrogel?
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Seem that a lack of common standards about studies of Nanoparticles cytotoxicity and others nanomateriais for interaction with living cells has been one of the limitations of the current research, mainly in neurosciences, which invoves diifferent cell lines, exposure times, and colorimetric assays that usec in different studies. For this reason, I think that it is necessary we beginning a discussion about this theme so that will be possible to compare cytotoxic effect among these results, such as single standard meets all conditions for obtaining information on nanomaterials cytotoxicity. What do you say about this theme?
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Also try: ASTM STP810  Cytotoxicity Testing: Prediction of In Vivo Toxicity from In Vitro Tests Published: Jan 1983 http://www.astm.org/DIGITAL_LIBRARY/STP/PAGES/STP30156S.htm
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I need to analyse the mechanical properties of Ochlandra species mainly by determining the tensile strength.Can anyone suggest me a good method?
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Hi Nisha, I could find some articles in Google Scholar. Hopefully you should be able to find more related to your requirements.
  • Yamamoto, Naoyuki, Akihiro Takahashi, and Toshinobu Toyohiro. "Tensile Properties of Natural Bamboo Fiber at Testing Temperature up to at 473 K." International Journal of Innovations in Engineering and Technology, Special Issue–JTL-AEME (2014): 37-43.
  • Sakaray, Harish, NV Vamsi Krishna Togati, and IV Ramana Reddy. "Investigation on properties of bamboo as reinforcing material in concrete." International Journal of Engineering Research and Application 2 (2012): 077-083.
  • Sukmawan, Romi, Hitoshi Takagi, and Antonio Norio Nakagaito. "Strength evaluation of cross-ply green composite laminates reinforced by bamboo fiber." Composites Part B: Engineering 84 (2016): 9-16.
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i am in need for more information about nitinol fabrication if you help me i will be grateful. 
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For example, look the review report  Ming H. Wu. Fabrication of Nitinol Materials and Components // Proc. of the Int. Conf. on Shape Memory and Superelastic Technol., Kunming, 2001, P. 285-292. All the best
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I am working on project with tissue transplantation within a collagen matrix. The described protocols in other studies are not working to control the final ph in the matrix. Please, I really appreciate any help.
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Hi
Can you please explain what kind of collagen matrix that are u using. 
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Tissue engineering has long worked on cartilage regeneration and several requirements have been identified for the engineered structures to meet the desired function that one of them is biodegradable and biocompatible scaffold. I want to know about the properties of hydrogels that we can use as a scaffold for cartilage healing in tissue engineering.
Thank you in advance,
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Most tissue engineered replacements for articular cartilage fail not because of choosing the wrong scaffold material, but rather inability to bear compressive loading or conversion to fibrocartilage due to excessive vascularity.  The former suggests that a uniform scaffold is not ideal, but a scaffold that reproduces the fiber orientation of native articular cartilage might have a chance of success.  I would look into a composite made of load-bearing long-duration (even non-resorbable) polymer fibers formed into the inverted U-shape of native Type II collagen fibers, surrounded by a gel that anchors the chondrocytes to the load-bearing fiber mat.  The gel composition could include an anti-angiogenic factor.  These ideas came out of my PhD thesis work on bone morphogenesis in the 1970s; I have looked at the literature since and found few papers exploring the concept of design for initial load-bearing.
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Hello everyone,
I often work with hydrogels and in many cases I have small pieces of plastic tubing embedded in the hydrogel. I am not very well versed in the terminology around this subject, but I would like to know how I can improve the "adhesive" force between the plastic and the hydrogel. I flow liquid through the tubing and I would like the space around the tubing to be as liquid-tight as possible, with the goal during flow conditions being unidirectional flow, and no backflow back out around the tubing. Since the hydrogel is mostly water, is what I'm asking an accurate description of what is possible? I am currently using perfluoroalkoxy (PFA) tubing in fibrin, transglutaminase-crosslinked fibrin-gelatin, and collagen hydrogel. We treat the PFA tubing with a concentrated solution of poly-L-lysine for several hours but I am not even sure if this is accomplishing anything since we have not thought of a way to test it.The PFA tubing is what we had on hand, but we would consider tubing of a different material or other chemical treatments. I would appreciate any comments or suggestion, as well as any references. Thank you!
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You could use a thin layer of agarose for fixing a piece of gel on plastic/glass surface if conditions of experiments allows it.
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We are working in this area and we thought that may be since they came from lignocellulosic background, they might conjugate with severla molecules. But not so convincing for us too this fact. Can any one help us to get the answer. We are getting around 50 surface where particle size is around 60-70 nm.
Surprisingly their supercapacitance results were excellent..
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IT is already reported in literature that lignocellulosic materials when pyrolyse they do exists like islands not coming as separate layers like graphene. This might be the situation when measuring exact surface area. This argument is given by several groups when they are working with low surface area materials mainly based on lignocellulosic based. I want better argument than this just make this more clear.
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Invitro studies , in the sense MTT and DNA Quantification assay is sufficient or need to perform any other studies..I am going to perform Invivo studies only with the scaffold not with any stem cells..
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Dear Thanusha,
In my opinion, before you perform in vivo study, you should evaluate the following parameters: cytotoxicity of scaffold, cell adhesion, proliferation, differentation as well as you should estimate whether you scaffold induce (or not) inflammatory during cell-biomaterial interactions. If you obtain promising results, your scaffold may be allocate to in vivo studies.
Moreover, I have a question and some remarks. Do your scaffold consist some absorbent components? If yes, you should not use MTT test in order to evaluate mentioned above parameters because obtained results will be unbelievable. So, for example, WST-8 assay is a good choice. Moreover, if you will stain the cells with dye, i recommend to use dye that not only distinguishes live/dead cells (AO/EtBr) but also reveals cell morphology (shows cytoskeleton)- for example AlexaFluor635-phalloidin.
I suggest to read the following publication, where you find apprioprate details about cell cluture experiments (cytotoxicity, proliferation, differentation as well as cell staining):
Klimek K, Przekora A, Palka K, Ginalska G. New method for the fabrication of highly osteoconductive b-1,3-glucan/HA scaffold for bone tissue engineering: Structural,
mechanical, and biological characterization. J Biomed Mater Res Part A 2016:00A:000–000.
Good luck:)
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I am planning to find the diffusion coefficient of PVA hydrogel.  what are the different methods available and how to find that?
 
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So you are actually looking for the diffusion rate of the film in water? Or are you looking tho find the diffusion rate through the film of PVA? If yes what is the permeate ?
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Folic acid is soluble in 0,1 M NaOH and Chitosan-g-folic acid is soluble in acetic acid. If I try to prepare the calibration curve, what solvent I have to use?
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Thank you!
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In Material and cell point of views.
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Final comment
The questions of risk associated with tissue engineering have recently been discussed in detail by a committee of the European Commission, culminating in a report on this subject14. The following is a summary of the main issues.
The basis of the report is the perception of the need for a careful analysis of the risk-benefit equation whenever a new concept of medical therapy is introduced into health care practice, such that this analysis can inform the development of regulatory control and clinical experimentation.
It is, of course, necessary to put this into perspective. Tissue engineering does not carry the same level of risk as xenotransplantation since the risks are confined to the patients themselves and not to the community at large, as may be the case when live, potentially infectious animal cells are used. It may also be argued that tissue engineering could be associated with less risk than conventional medical devices or medicinal products, since the latter are mass-produced and the hazards related to defective products or unforeseen mechanisms can affect thousands of patients. Tissue engineering is essentially a customized process that, although involving some commercial components, is directed towards individual patients, minimizing the scale of the hazard.
On the other hand, tissue engineering, as with cell and gene therapy, involves the manipulation of live cells and the interaction of these cells with substrates and biomolecules in unusual circumstances, leading to the possibilities of contamination, process errors, and as yet unknown cell-substrate interactions that could have serious consequences. The analysis of risks and benefits has to take into account the fact that some applications carry very high risks for the patient but address immensely important clinical conditions, while others are aimed at non-life-threatening conditions for which there are already adequate treatment methods available. In other words, both risks and benefits vary considerably. The nature of these risks to patients may be enumerated and summarized as follows:
Microbiological contamination associated with source materials, including the possibility of latent viruses, which may give rise to infectious diseases. This may have to be addressed by the exclusion of certain types of donor for allogeneic products and the archiving of source material will be important.
Disease transmission, where some disease states such as cancer, blood disorders, and genetic conditions will have to be considered.
Contamination associated with the production process, generally of low risk and addressed by standard operating procedures and quality systems.
The delivery of unwanted cells, especially in coculture situations, resulting in ineffective products.
The risk of mix-ups, especially with the use of autologous cells and the delivery of the resulting tissue to the wrong recipient.
Risks associated with the modification of cells during the processes of cell amplification or differentiation, especially those involving genetic manipulation.
Risks inherently associated with the scaffold and with as yet unknown cell-scaffold interactions. It has to be said here that the development of scaffold materials has tended to follow on from the applications of materials in implantable medical devices, which is not necessarily the best approach. There are still many risks of underachievement with respect to the quality of regenerated tissue because of failures to understand the specific biocompatibility requirements of tissue engineering scaffolds15.
Risks associated with the achievement of sterility of the final product, which may be a complex combination of cells, materials, and biologically active agents.
Risks associated with the potential toxicity of cryopreservatives, process additives, and other residues, as well as patient-specific responses such as allergies to antibiotics or other substances.
Risks associated with the performance of the final product. There are risks that the regeneration process may not yield tissue with adequate mechanical or physical properties, which could result in life-threatening situations, for example with tissue-engineered blood vessels or valves.
The combination of risks identified above contributes to the uncertainty that currently exists with respect to the commercial and clinical exploitation of tissue engineering. It should be noted that, during the last decade, a number of companies have been formed with the objective of commercializing tissue engineering and at one time investment in these companies looked attractive. However, that tide has profoundly turned and there have been a number of high profile bankruptcies and changes in company positions over the last few years, with little hope of recovering initial investments. Two fundamental issues are at play here16. On the one hand, the research and development costs are extremely high. On the other, there is little prospect of these companies being able to sell their products and processes for a reasonable sum. Even when they are in the market, the treatments are usually labeled ‘investigational’ or ‘experimental’, which means that the treatments may not be reimbursable under most insurance schemes. The question arises as to whether tissue engineering will ever be deemed cost effective. It is likely, for example, that the cost of treating diabetic foot ulcers through a tissue engineering approach will run into the tens of thousands of dollars. The cost of alternative treatments, i.e. keeping the wound clean and applying wound dressings, may amount to a few dollars per week. We have, therefore, a situation in which the costs of the development of tissue engineering and regenerative medicine will have pharmaceutical dimensions, but with rewards that will be similar to those associated with the conventional medical devices they are replacing. The dilemma is easy to see. The solutions lie within a complex array of technological, political, and socio-economic factors, the evolution of and interaction between which will be interesting to watch over the next few years.
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We are trying to understand how capability of 3D tissue scaffolds made of polymers and ceramics is affected by their internal architectures. Currently, we have obtained a series of micro-CT images (about 300) of a polymer-made scaffold. We want to use imageJ to achieve 3D reconstruction and get to know overall porosity, surface area and distribution of pores and ratio between open and closed pores. 
I wonder if there are any imageJ plugins can do this. If not what other software can be used?
Your help will be very appreciated. 
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HI,
If you have Micro CT software, I think you can achieve what you want to see. Basically, micro CT software can reconstruct 3D Images and you can see clear of pores properties.
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Hi everyone,
I've been interested in spider silk lately. There is a question that puzzle me for a while.
While mainstream papers underlines the advantages of spider silk over other materials (like steel and nylon), few of them mentioned the comparison between spider silk and other insect silks(like silk of silkworm). My question is : is spider silk outperform other insect silk as biomaterial (specially biomaterial for engineering). If yes, how?
Thanks,
Guangqi
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Hey there, Guangqi if you wonder spider silk is far better than the other silks woven by the other insects,you are absolutely correct. Spider silk is so strong that if we this biomaterial is properly used or synthesised we can build a lift which can go to the moon and come back to earth. The strenght of the spider silk is due to it's composition.
The spider silk constitutes of  fibroin (Mr 200,000-300,000) which consist of spidrion 1 and spidrion 2 and 42% glycine and 25% alanine as the major amino acids.
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I need to study release profiles of the scaffolds containing GAG's...is there any method?
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Hi Thanusha, you can do the papain digestion followed by estimating the GAG content by DMMB method.
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Hi! I am currently working in the development of a synthetic material formulation to form tube-like structures by seeding HUVECs on top of the material. The goal is to have the tube formation always take place at the same time, instead of at different time points as I saw previously with Matrigel.  I already have some organization of the cells, which indeed happens always at the same time; now I would like evaluate/rate the quality of the network formed, anyone has a suggestion of tests or markers to perform this characterization?  Thank you very much.
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In my opinion, the best characterization is to stain your cells for endothelial markers such us Pecam-1 and to perform confocal laser microscopy with 3D reconstruction. Also, you can monitor angiogenic behavior over time (real-time) to support your observations.
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I have been working as a member of a research group in the field of cardiovascular stent. We prepared our 3D-printing stent with a reasonable mesh-like structure. But before any further surface modification, we need to investigate its mechanical properties, and conduct the mechanical testing on our model stent.
I need to know what type of analysis testings we need to be run.
I would be happy to hear your answers.
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Dear Setareh
I think you can go for these tests:
- Volume Fraction
-  weight fraction
- Elasticity test 
- Destructive Test which include( Tensile Test, Compression Test, Torsion Test , Bending Test, and Hardness Test)
- Non Destructive Test(NDT) which include :( Visual Technique, Liquid Penetrant, Ultrasonic Test ,  Impact Resonance, Pulse Velocity, and vibration dampingtechnique).
 Regard
 Raid
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For example, between neurones there are electrical signals, but these electrical signals there are in all type of cells, like the smooth muscle cells. In tissue engineering, the scaffold is use to make a support for the celular proliferation, normally this material is insulating. But, what would happen if the scaffold is make with a conductive material? the cellular comunication will be better? (without electrical stimulation in vitro, that's another topic).
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Hi dear Gopinathan, thanks for your answer. Im going to download your paper.
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I need some information about the chimical composition of mussel seashell.
Physical and geometrical caractérisaion of Mussel seashll. 
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Thanks, Mr. Mushtaq Ahmad
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I have bleached and treated my cellulose..I found out that if i air-dry it and when want to proceed with second cycle of treatment, the cellulose will agglomerate and form pellet-like form..
So, what is the best method to keep it?
Thanks
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thanks all
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Mesenchymal stem cells are seeded into chitosan/k-carragenan scaffolds. What assay can I use to evaluate type II collagen formation as to confirm the possible effects of the scaffolds in the chondrogenesis of the MSCs? Thanks! 
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Hello Mdee,
As per my experience you can use collagen type II antibody and can observe the deposition of collagen in cells by fluorescence microscopy by typical immunostaining protocol. Deposition of ECM proteins can be easily observed by this technique and it is most potent and versatile technique to see matrix deposition qualitatively as well as semi quantitatively.
Hope it helps !
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I need a way to functionalize silk fibroin with Ag or Quaternary ammonium.
My goal is to electrospin functionalized fibroin to obtain an electrospun mat that doesn't release Silver if it is put in water (or another liquid).
I tried using sulfadiazine in solution with fibroin and formic acid, but there's release of silver when I put the mat in water.
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You may use a silver nanoparticle solution alongwith the spinning solution so as to get a composite mat and the Ag being in nano scale may not spill out when immersed in water
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Hi All, I have seen various papers regarding grafting of Methaacrylate anhydried on Gelatin for photocroslinking. I am curious that Acrylate grafted group has unsaturated Alkene(C=C) end chain, and can we crosslink this Alkene ( c=c) group with primary amine or other functional groups with or (preferably) without photocroslinking method .... Can You suggest me the protocols if Any..
Thanks In Advance
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Gelatin acrylate plus PEG divinyl sulfone (or PEG dithiol) may be crosslinked through Micheal-type addition reaction. Gelatin Methacrylate can be less effective than Gelatin acrylate. However, photocrosslinking by U.V is mAdd your answeruch faster than normal chemical crosslinking by chemicals.
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If I buy a titanium sheet, does it already has a thin layer of titanium oxide or should I sputter a layer of titanium oxide on it after cutting?
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Hi, titanium sheet should have  about 25 nm thick native oxide or more.
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Direct delivery to tumors remains a problem in most nanoparticle applications because the immune system rapidly removes circulating nanoparticles by ultimately accumulating them in the liver and kidneys. Can nano graphene oxide with enhanced tunable fluorescence be used as bioimaging probes without attaching antibodies?
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It may be possible to self image the tumour cells with GO via chemodosimeter technique via selective ion channels in cancer cells. GO assisted chemodosimeter for detection of fluoride ion (carcinogenic) has successfully been developed. For details one may follow the link
Same approach may be utilized for selective detection of ion channels present in cancer cells.
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My research focuses on electroactive polymers, and especially on IPMC. I am looking currently on making IPMC using platinum. Any help will be appreciated.
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I'm not too familiar with trying to increase the blocking force. It looks like using Palladium in the the hydrolysis step may work to improve by ~1.5-2 times, see this reference for more info: http://dx.doi.org/10.1088/0964-1726/17/3/035011
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Suppose a single strand oligonucleotide (a 50mer) is fixed onto nylon membrane by UV crosslinking, afterwards hybridization is executed to obtain double strand DNA fixed on nylon. At this point, I need to separate the two strands to obtain again the initial single strand DNA fixed on nylon. Which method would be better suited for this experiment?
Thank you,
Giuseppe
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DNA design and strand displacement by using a third strand?
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We are running this in-vivo experiment that involves coating of vicryl suture with a protein to assess its effect on wound healing. I would like to confirm that the coating was successful but to do this, I would need to chemically detach the protein from suture before ELISA.
I would appreciate suggestion from anyone with experience in this.
Regards
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Hi Evaristus, I have to admit that I am not familiar with vicryl sutures, but looking at the structure, I'm inclined to say that the proteins can form amide bonds by protein primary amines attacking the C=O bonds.   
If there is a covalent bond formed, then proteins will not be detached by boiling in 1% SDS. They will be detached when incubated with trypsin or proteinase K.
(BTW I'm in lab 130 at BRI, so we can talk)
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Have effectively used DAPI to mark hematopoietic nuclei in polyurethane scaffolds, but when using phalloidin to stain F-actin the polymer scaffold also uptakes the dye and it becomes too difficult to discriminate cells from the polyurethane. Anyone have a similar issue? I am looking for a stain to highlight the entire cell body.
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Cell tracker green CMFDA is a non fluorescent probe in nature. Upon internalization into the cell it is modified and becomes fluorescent and trapped in cytosol. Since it is not fluorescent before metabolization it will now fluoresce when bound to PU. You have to stain the cells prior to fixation, since metabolization of the dye molecule requires live cells (it is a live cell stain). After dying the cells alive you can fix them and permeabilize for further processing. Dye does not leak after fixation. Green excitation/emission spectra (492/517 nm maxima). Similar to FITC or alexa 488. Since it is metabolised and trapped in the cell, it dyes whole cytosol including nuclear space (all the liquid components).
We had a similar issue with collagen and this helped a lot.
Good luck.
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Dear colleagues. How can we  fixe a thin layer of hydroxyapatite on flexible implant (e.g., flexible intramedullary nail) and to avoid the loss of HA bending that implant?
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deposit on rough titanium
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Swift improvement on Bioprinting, but how to organise and "functionalize" printed cells? To take the "growth" strategy mentioned in your book Extreme Tissue Engineering?
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Hi, one way to organise the cells is with electrical stimulation, you can verify some articles with this topic: "electrical stimulation in tissue engineering".
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People say that the capacitance involved in the organic electrochemical transistor is not simply the double layer capacitance in between organic semiconductor and electrolyte but it is a volume dependent capacitance (F/cm^3). What is the physics behind this capacitance ?
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I think if you go back to first principles and think of the definitions of charge, integrate to get electric field and integrate again to get voltage with the geometry you have you can start to develop the idea. You also should consider that the total distribution of charge should be neutral. Then look at the definition of capacitance relating charge to voltage. I think you would have  a contribution from the charge at the interfaces, and then if you have charge trapped in the volume between the interfaces you would have a contribution in charge per unit volume. 
In the regular semiconductor it is likely that it is a good approximation that just the charge at the interfaces is enough, unless you have a material with a lot of bulk traps, Where in the organic semiconductor depending on the material if may have more ability to trap charge with-in the bulk of the material, or the charge distribution from across the interface has a non-negligible depth to maintain charge neutrality.
This is off the top of my head, I haven't looked at organic devices in many years, and I am not sure what device structure you are considering, but the approach should be sound.
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i intend to prepare activated carbon from some biomaterials. i am trying to employ a mixtuere of two popular activating agents to produce activated carbon and then make comparism with indiviual activating agents. please does anything such as coactivating agents exist?. your answer will assist me in a long way. thank you
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One activating agent is always more efficient than another one, depending on precursor, temperature, concentration, and time. If you mix 2 activating agents, I am not convinced that you can observe any synergetic effect, but instead it will be difficult to explain the resultant porous structure. If one activating agent is much less efficient than the other (e.g. comparing a carbonate and a hydroxyde), the efficacy will be decreased as the best agent will be diluted. So the possibility exists (unless you mix phosphoric acid with KOH, which would be a very bad idea !), but I am not confident in the result.
Alain
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Hi,
I want to mesh a femur with hexahedrons, but I am not able to do it, since Comsol uses tetrahedral elements by default. I cannot  use the sweep feature due to the geometry. Could someone help me?
Best wishes, Murat
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Hi. you can use CST studio frequency/time domain.
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Hi Can anybody recommend a good, current micro/nano fab text books for graduate level class? Recommendation of books regarding Micro/nano structures for biological science would be also welcome. 
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Try this, its a good handbook especially for nanobiomaterials. I have attached the intro chapter here if you are interested. 
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are there any specific substrates, which are used for cell growth for tissue engineering? if say glass is used, how the cells attached to its surface, say through the proteins, get the required nutrients for growth? what are the essential requirements for such substrates?
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Dear Sunita Mehta,
When you say substrates used for cell growth in tissue engineering, are you asking for substrates used to expand cells before seeding them on a scaffold or are you asking about typical materials used for preparing scaffolds?
Very briefly.
Typically, T flasks are used (attached link) for cell expansion, which are made of polystyrene with a treated bottom surface to allow cell adherence.
Regarding substrate culture conditions, there are 2 types of cells: adherent (the big majority) and non-adherent. The first group of cells does not survive if they do not have a surface that allows them to adhere. This big group of different cell types has proteins on their membrane called cell adhesion molecules that allows them to anchor to the substrate (if it is compatible). The nutrients that they consume are provided by the culture medium you add to the flask, there are many kinds, and it should be also compatible with the cell type being cultured.
Regarding materials used to produce scaffolds, there are many to say the least, from natural to synthetic origin, from hydrogels to ceramics...
I wish I could help you more, but you have to be more specific. I advise you to get a book on tissue engineering and start from there.
Best regards and the best of luck with your research,
Sebastião van Uden
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When the hydrogel is stretched to 2000%strain, the clamp of test machine could not grasp the hydrogel and the hydrogels slip. is there any method to solve this problem?
thank you!
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The tension on the narrow section is so high that the grip portion of the hydrogel (and its frictional force) is not able to keep the hydrogel in the grip.  Assuming you're not restricted to a particular ASTM test (which specifies the sample geometry), here are two things you can try:
1) make the "narrow section" of your sample specimen even narrower.  This would lower the tension at the 2000% strain.
2) If you have a screw grip (i.e. constant pressure): make the grip portion of your hydrogel larger.  then more grip area = more normal force = more frictional force.  You can also tighten the screw more (without destroying your sample, of course....)
3) If you have a pneumatic grip (i.e. constant force): increase the pressure on the pneumatic grip (without completely deforming your sample....), so that your normal force is greater.  Then you'll have higher frictional force.
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I have PDMS microcasted molds attached to a photopolymerized sacrificial mold. Is it possible to dissolve the photopolymerized material?
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Use UV crosslinkable polymer which form reversible crosslink. Bisbenzylidene based polymers and other polymers making cyclobutane ring during crosslinking can be used which is crosslinked at 365 nm and uncrosslink at 254 nm. I believe your sacrificial mold will not have any problem.
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Which force is needed to make an implant move/grow through soft tissue? There seems to be a threshold to be overcome by stents (or other implants) to make them grow through tissue. Too low means no growing through. Too high would create lesions. The only reported force I know is from bracelets on the teeth (nearly constant 1-2 N for extraction).
Is there anything known for soft tissue? Ideally for stents in atrial walls? Which biological processes enable this kind of "growing through"? How could i foster it?
I'd be thrilled to hear about your input!
Johannes
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Conventional arterial stents are designed not to grow into the intimal, medial or the adventitial layers. The stent is designed to distribute a uniform radial force sufficient to hold it in place reliably. Restenosis is and undesirable consequence that presents as a growth around the stent. If you want a stent to 'migrate' through the artery wall then it must be designed for that purpose. The form factor and profile for each strut should be reconsidered. Other considerations would be the edge effect of outward radial forces and perhaps other means of constricting the artery to provide a reactive force. These can be mechanically or pharmaceuticaly induced.
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Hi dear fellow researchers,
I am trying to estimating the corrosion rate of coated steel vs uncoated one by polarization techniques (Tafel slope extrapolation and polarization resistance). I am new to this field.
Am wondering, during this kind polarization test, whether we should stir the electrolyte or not. I tend to think that I should stir, as the theory requires that the electron transfer at the solid-electrolyte interface is fast and thus does not limit the current (compared with supply of electroactive species to the interface). However, a search using scholar.googe.com showed that, only very few studies mentioned stirring in their polarization tests, suggesting in most cases the electrolyte was stagnant. 
I am curious why? In my limited polarization experiment, the current produced a lot of bubbles (O2 in the anodic branch) clear visible to the eye and attached to the sample. Don't these bubbles prevent molecule/ion transport to the sample surface, thereby limiting the current?  I am a bit confused here.
Another point I am missing is that, the Tafel (or Volmer) theory suggests that extraplation of the Tafel slope (if it is indeed a linear region) to the open-circuit potential you will get the corrosion current. Thus, theoretically we can determine this current (Icorr) from only one branch (either anodic or cathodic) of polarization. Again, search shows that most studies performed scan covering both cathodic and anodic branches. I am curious that, is not a scan starting from open circuit potential to either side sufficient?
Since I am new to this area, pls feel free to instruct and "school" me. And thank you very much for your help.
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I have no experiance
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I have to know the viability of cells encapsulated in a hydrogel.
I've tried to study the viability of cells encapsulated in a hydrogel with alamar blue but I think that resazurin doesn't penetrate in the hydrogel and hydrogel interferes with the fluorescence of resorufin.
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even we have faced this when using hydrogels.. and it also depends on th etype of material, it worsens the situation..
I would advise you to make very very thin films of cell encapsulated hydrogel, and can use LIVE/DEAD assay.. confocal microscope will give you better  image and you can 3-d stack..
another way, after encapsulating cells in hydrogel, after specific time intervals, make crysections of the hydrogels and stain for any cell viability markers.. but this will be more time consuming and expensive.
Another way is, if you are able to dissolve the hydrogel in some cell compatible solutions, or if you are able to remove the cells from the hydrogel using some enzymes, then you could easily quantify... seems complex, but have to work a way around when working with hydrogels considering the time, cost etc..
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After immersing my sample scaffold (Gelatin-Chitosan-TCP) for 10 days i got lots of crystalline particle along with small amount of apatite. EDX analysis shows that majority of this crystals were NACL. Why this NACL precipitate in SBF study??
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Thank you sir for your valuable suggestion.
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Hi, I am working with isolation of primary osteoblasts from different sources to study their interaction with biomaterials. I recently isolated cells from neonatal mice (i day old) calvaria. I am not sure if they are preosteoblasts? and do they require ostegenic medium (i.e alpha MEM supplemented with ascorbic acid, glycerophosphate and dexamethasone) to become functionalised osteoblasts (which can form bone nodules)?
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wow, Thanks heaps for the information! 
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I did GAG estimation for native tissues and decellularized samples by DMMB method. Decellularized samples are showing high content of GAG protein than in the native tissue. Is the DMMB reagents reacts with the detergents or the cellular lysate? Give your suggestions please
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 Dear Janani, both the above are correct. We also observe the same with pig liver. If you want to  get meaningful results you should carry out the GAG and collagen quantification in samples which are fully swollen in PBS or other isotonic solution. In that way the "holes" you make when decellularising are filled with water, so the tissue mass remains essentially unaltered before and after cell removal. We have described this method in our paper. 
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Cell: Eahy 926
Scaffold: gelatin foam
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Dear Mahua
First attached your scaffold on the plate (with fibrin glue) ,second the cells (1000000 in per ml)drop on your scaffold.
Sincerely 
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I am working on a photopolymerized hydrogel thin film project using the electrospray method. Does anybody ever use this method? I plan to use PEGMA and EGDMA as a crosslinker. And derivatives of acetophenone as the initiator.
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not really, but i am trying to use the method as stated in below. they pump a solid suspension and electrospray it onto a substrate. However, i am completely noob to this technology.
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What is the solvent suitable for dispersing MWCNT in PVA? How to disperse the MWCNT in PVA solution?
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The best way for the modification of MWCNT by acid treatment.It can be easily disperse .
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Hello
I have prepared chitosan film forming solution by dissolving 2g chitosan at 100ml acetic acid 1% and after stirring and good dissoving I want to remove any undissolved particles by whatman  paper no. 3 that is used in an article (Development and evaluation of a novel biodegradable film made from chitosan and cinnamon essential oil with low affinity toward water) but for its high viscosity it didn't pass from paper. I used the papers no. 2 and 1 but the result was same. I used centrifuge by 15000 g and there was no sedimentation. Can you help me how can I remove the undissolved particles?
thanks 
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Thanks for all your answers.
Fortunately I solved my problem. First, I heated film forming solution to 60 C and then I filtrated it by using a vacuum pump and whatman paper no. 3. It got 6 hours for 800 cc.
thanks.
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I'm trying to develop a hydrogel which can release proteins at a controlled rate.
I'm currently using 4 arm PEG maleimide (10 & 20 kDa) and 2 kDa PEG dithiol has the crosslinker via micheal type addition reaction.
According to Zustiak and Leach (2010) Biomacromolecules, 11, 1348-1357 - the Mw of a crosslinker is related to the degredation of the hydrogel. they have results showing hydrogels crosslinked with 8 kDa crosslinker  degraded faster then 2 kDa crosslinker.
So am i right to assume if i use 1kDa PEG dithiol the PEG Malemidie will be more stable?
Has anyone used other crosslinkers apart from PEG Dithiol?
Thanks.
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If the gel is strongly crosslinked, the crosslinked density is just the inverse of the number of monomers between two consecutive crosslinks. Now, for weakly crosslinked gels, this density is essentially the inverse of the molecular weight of crosslinked chains.
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please see the pictures.
I want to know about overlap and fusion of fibers in the C part in attached picture. it can cause changes in the mechanical strength of electrospun scaffolds? how?
increase or decrease? 
can you introduce an article to me? thanks
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Based on your results, I would say the compliance of the fused or linked fibers got decreased; and additionally, the ability of the fibers to align together under loading got decreased, those things gives rise to the decrease in strength.  To look into these effect, you should quantitatively characterize the geometry of the fibrous network and the density of the fusion and crosslinking, etc. 
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In porous metallic implants, the interconectivity of pores is so important for cell nutrition. and open cell foam is much better than closed ones. but how to measure the interconectivity of foams?
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salam;
the test of interconnectivity is a complex one,,,bear in mind that most of the techniques usually disclose the porosity without measuring interconnectivity!, but the total porosity is as follow:
totol porosity= micro/macro porosity + interconnected porosity
some techniques that may be useful:
A> fluid displacement method: 1. Gravimetric calculation based on density/gravity; 2. volumetric method using mercury porosimeter machine (but these methods show only the total porosity without distinguishing
B> use of imaging technology such as CBCT, SEM, TEM,,,to show you 3D tomography (these methods may be more appropriate)
best
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I need to visualize the CMFDA/PI stained cells within the scaffold, but dehidratation steps needed for paraffin embedding of the samples partly erose my PLGA scaffold. I read in many papers that they use paraffin embedding with this kind of scaffolds, but no one says nothing about the protocol used. Another way could be to use OCT instead of paraffin, avoiding dehidratation steps. Any suggestion?
Thank you in advance!
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yes I would suggest use cryo sectioning, Use OCT medium and liquid nitrogen,
Cryo work for me I used porous chitosan samples with hydroxyapatite
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 mainly for  b. mori silk. sericin is a gummy substance which is soluble in hot water. Then why there is need to treat with chemicals like soap solution, sodium carbonate etc.
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Sericin may be in a fairly stable conformation when coating the silk fibers (acting as the "glue" in silk fiber networks). Such stability could arise from the forces between the sericin proteins (like hydrophobic interactions), and just treating with hot water may work but is probably a quite ineffective way to remove all sericin proteins from the fibers. Adding chemicals like various soaps or salts can reduce the interaction between the sericin proteins and yield a more effective denaturing/change of conformation of the sericin, which leads to a more effective removal. 
ATR-FTIR is applicable to most materials that can be analyzed with FTIR in transmission. There are a few studies for how the FTIR spectra depends on the sericin/silk fiber ratio: 
Production of silk sericin/silk fibroin blend nanofibers: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3212049/ 
Using FTIR spectroscopy to detect sericin on historic silk: http://link.springer.com/article/10.1007/s11426-010-0050-y
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Hi everyone,
I'm interested in flow through a collagen scaffold. I am thinking of using needles to insert into the collagen scaffold hooked up to a peristaltic pump. Has anyone done this before and what have you used to secure the needles into the collagen so they don't fall out or leak? Are there any alternative methods?
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Why do you want to put needles in it ? There is commercial system for the seeding of scaffolds. for instance this one : 
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I want to know the required thickness of a 3D scaffold for tissue engineering.
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It really does depend on the type of cells you are trying to seed as well as the application and potentially whether you want to trap any cells in or out of the matrix while allowing diffusion of certain agents.
There are a lot of good resources to read on the matter, but I suggest you start here:
Best of luck!
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In my study, gentamicin sulphate increases the setting time and decreasing the reaction rate of chemcal cured dimethacrylate composite system. i am trying to find what are the possible explaination for this increases in setting time ? can sulphate reacts with the initiator or activator or incorporation of air bubbles with the addition of gentamicin sulphate might be the possible cause.
thanks in advance
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The main issues I work thermal spray coating and welding.I worked as an investigator in Biomaterials. Prof. Dr. Faik Nüzhet Oktar gives a much better answer your questions about  Biomaterials.   Thank you for your attention.
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biomaterial
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Dissolve the PCL in chloroform then add dropwise to a well-stirred solution of water containing some poly(vinyl alcohol). The size of the particles depend on several factors: concentration of PCL solution/stirring speed/concentration of PVAlcohol in the water so these need to be carefully controlled. But if this is done can get pretty good control of particle size.
Good luck - George Roberts
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How would one keep track of sample orientation. How do culture cells in a well so that one can then transfer it to a specimen mount. Is there some kind of special insert one can put in the well. Or would one fix and dehydrate in culture dish, plate,well, etc and then transfer it to the specimen stub? I am using glutaraldehyde as my primary fixative and osmium tetroxide as my secondard, so any material would have to be compatible with those.
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1. You can use Thermanox coverslips (for example like these: http://www.emsdiasum.com/microscopy/products/preparation/plates.aspx#72274)
Very handy.
2. You can process your sells in wells (fixation, dehydration, etc) and then cut out bottoms of wells with hot scalpel blade (will not work for CPD, but in many cases suitable results).