PDT - Science topic

Stating that the photosensitizer effects have two types. 1) Direct effect 2) In-direct effect.

I am interested to know if there is a photosensitizer that is generating substantial damage by PDT type 1 without relying on oxygen. I want to use this molecule for studying DNA damage in a hypoxic effect on the microscope.

Dear Accademia, I received the PDT and SPE files of the XPS results, but I couldn't open any of them. Please suggest the possible software opening these files?

Photodynamic Therapy is underestimated as clinical option and even ignored by health systems and facilities worldwide, notwithstanding decades of reports of excellent and advantageous results in a plethora of applications. It is time to debate about resources and tools for education and knowledge on PDT, particularly aiming students of medical and related schools. It would be worth if scientists and practitioners could contribute with editorials, letters and comments bringing this debate to the spot light. In this regard, I would like to share some contributions:

I am doing a three point bend test with concrete specimen of dimension 280mm*90mm*90mm. I am putting 2 sensors near the notch with 3cms away from both the sides. the experiment ran for 20 mins but i am getting either 50 or 90 hits with 1 or 2 events. I am not understanding what the problem is. I have set threshold = 40 , gain = 40db when I am doing lead break test I am getting hits from both sensors events are obtained sporadically. HDT,PDT and HLT values are kept by default which are suitable for concrete. So I do not understand what is the problem. Please I need help

Most studies using In vitro 5-ala photodynamic therapy model uses a serum-free medium while incubating with 5-ala. It is actually sensible that the presence of albumin in serum can interfere with 5-ala absorption and activate ABCG2 to efflux ppIX out of the cell. We have observed in the lab that using fbs containing medium can increase the LD50 making cells less sensitive to PDT compared to when cells are incubated with serum free medium. This goes to show that PPix levels are theoretically different between those two scenarios. Moreover, difference in manufacturing of fbs even of the same brand could also yield inconsistencies of results. We have also observed that using fbs last year and this year, and also within co labmates, had different results. Therefore we used serum free all throughout the experiments.

However, if we will think in vivo, cancer lesions contain more albumin due to increased vasculature. Simulating this in vitro would definitely demand that we use fbs instead. In your opinion, what is your take on using serum free medium in the protocol? Would this be a factor to criticize the in vitro model (no fbs was used)?

As both Chlorophyll semi-synthetic derivative and methylene blue organic dye has been widely used as a potential photosensitizer in applications like PDT but I want to know that; a chlorophyll derivative can photodegrade methylene blue by Type II photosensitization process or not?

Please provide me some reason if it is feasible then. thank you

I'm currently formulating my protocol for creating a resistant cell line against PDT. I'm planning to use a cancer cell line and expose the cells in several cycles of PDT. The cell line will be considered resistant if survival assay (MTT) will have 1.5 fold compared to the parental cells. My question is, how can I be able to test each cell generations with MTT assays if that cell generation itself must be subcultured to be exposed to PDT again. Could I make 2 plates in each generation cycle, one will be for MTT, the other one for PDT?

Thank you very much.

In general DNA targeted chemotherapeutic drug, interact with DNA and inhibit the DNA function finally cause the cell death (both normal and cancer cell). To understand the DNA binding ability of the drug DNA binding studies have been carried out.

But, In PDT, photosensitizer kill the cells in the presence of light. Then what is the meaning to study DNA binding affinity of the photosensitizer. Can't it inhibit the DNA function and kill the cell as normal DNA targeted chemotherapeutic drug?.

ok if the photosensitizer shows weak interaction with DNA then it won't kill the cell via DNA inhibition the cell death only cause by ROS generation. but many papers reported that photosensitisers show more intercalation interaction with DNA and said that ROS generation is main cause for Cancer cell death. Why not DNA binding affinity is not the reason for cell death.

Then what is the use for DNA binding studies? Is it just add more data to the article?

When I read the paper about PDT therapy, I found an interesting result that Phthalocyanine blue, one kind of PDT reagent, can be selectively retention in cancer cell for unknown reasons. Dose anyone know similar moleclues can be selectively retention in cancer cell? and the mechainism? Thanks.

Can anyone tell, I am doing cellular (4T1 cells) uptake with PDT, But after PDT the cells are disappeared during FACS analysis. My fluorescent dye is Ce6 in nanoparticles.

We observed "naked nuclei" in metastatics cell complexes of lymth nodes after theirs PDT.

I would like to implement spheroid-based screening in my research, but I'm have a hard time trying to treat my spheroids with the solutions of my compounds. Specifically, the main problem I'm experiencing is the removal of the culture media without loosing spheroids. This is the procedure I've used so far:

- Seed cells in P96-well plates (200 microliters of cell suspension per well) coated with 1.5% of agarose;

- After 4 days from cells seeding, remove 100 microliter of medium from each well using a multichannel pipette;

- Treatment with 100 microliters of a 2x solution of compounds;

- Irradiation;

- Removal of 150 microliter of the medium containing the compounds;

- 2x Wash with 150 microliters of PBS;

- 2x Wash with fresh complete medium.

During the removal steps I always loose spheroids, so I would like to ask if someone has any hints. Thanks in advance!

Methylene blue is widely used as powerful photosensitizer in PDT and antimicrobial photodynamic therapy. In the other hand, methylene blue is commonly used for DNA staining and sometimes it shows dark cytotoxicity/genotoxicity.

How can a DNA binder with potential toxicity deal with such selective photodynamic modalities??

Measuring TPA coefficient (two photon cross section) and non-linear optical refractive index using Z-scan method with pulse or CW lasers is routine. So, is two photon excited PDT by CW laser achievable?

I know that phthalocyanines require metalation to undergo intersystem crossing, therefore they can be used as efficient photosensitizers in PDT.

I am wondering if the free-base phthalocyanine are really used in PDT?? and what is the benefit of these free-base molecules??

Does anybody know a photosensitizer that has an absorption peak around 400-430 nm and soluble in water?

Thanks

It is proven that many bacteria species (e.g. H pylori) produce/metabolize porphyrines, that are natural photo-sensitizing molecules. Many other bacteria species, such as E. Coli, do not naturally "contain" such molecules.

I am interested in this second class of procaryotes.

Do specific protocols exist to make procaryotes (and in particular E.Coli) sensible to external light irradiation, by previous internalization of porphyrines or other photo-sensitizers ?

Literature on anti-bacterial PDT is huge. I'm looking also for advice on a comprehensive study of the light spectrum and dose dependency of PDT anti-bacterial efficacy.

Thank you.

If fibroblast cells had been washed and flushed the floating cells out before dissociation and staining process, should only viable cells or total cells be counted for PDT calculation ?

In our research group we are concerned with PDT. A reviewer of a paper asked us to compare our materials (which perfom well) to Photofrin.

Unfortunately it is really hard to come by, or so it seems. We asked a couple of hospitals in the area: no chance. Next we asked clinicians: no chance. The manufacturer was willing to send a dose for research purposed in exchange for exclusive rights on the research: a no-go!

I would be really happy, if somebody has a spare dose (maybe expired) that we could get. Or if somebody knew where we could buy a couple of doses from.

Thanks for your inputs

I want to coat rose bengal over the chitosan coated iron oxide nanoparticles to be used in a drug delivery/ PDT. 

Our lab is now facing a problem on how to synthesised cationic Gold nano particles. 

We established our own method to fabricate Gold nanorings by on substrate fabrication instead of chemical synthesis. We aim to combine PDT with PTT. So the first problem is to attach 5-ALA on gold nanorings. With the negatively charge surface ALA molecules, the most direct way to attach ALA on gold nano particles(GNR) is making a positively surface charge GNR. But most of the previous research synthesised cationic GNR by adding HAuCl4 and BPEI together to generate a cationic molecules. But we use different way to fabricate GNR. Therefore can anyone tell me how to synthesised cationic GNPs to attach on ALA?

Thanks!

I need a safe procedure as it involves radiation. I am working on PDT, which involves UV light exposure to cell cultures. I need to know a safe, simple procedure to do the same. The source of light will be a portable lamp producing UV rays. What measures to be taken to confine it to a small place and what safety aspects should I undertake, when performing the experiment.

I am wondering if the photosensitizer (PS) can be exited several times with light exposure when it retains in tumor for certain time delivered by a self-assembly system. if the PS is returned to the initial state (not  bleached during PDT) after sometime post-PDT, the retained PS can be exposed to light several times leading a continuous treatment.

What do you think about future of PDT (Photo-dynamic therapy) in tumors treatment? About its development and future?

We are doing some PDT works using devices from GenIUL, but in my point of view the use of IR are very interesting for some medical applications. I am not sure some commercial devicesexist in this wavelength. I think it's better to use commercial solutions, as we don't have time to spend developing experimental set-ups, especially if we are not engineers.