Weiliam Chen

CUNY Graduate Center, New York, New York, United States

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Publications (47)188.65 Total impact

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    ABSTRACT: Despite the prevalence of disc degeneration and its contributions to low back problems, many current treatments are palliative only and ultimately fail. To address this, nucleus pulposus replacements are under development. Previous work on an injectable hydrogel nucleus pulposus replacement composed of n-carboxyethyl chitosan, oxidized dextran, and teleostean has shown that it has properties similar to native nucleus pulposus, can restore compressive range of motion in ovine discs, is biocompatible, and promotes cell proliferation. The objective of this study was to determine if the hydrogel implant will be contained and if it will restore mechanics in human discs undergoing physiologic cyclic compressive loading. Fourteen human lumbar spine segments were tested using physiologic cyclic compressive loading while intact, following nucleotomy, and again following treatment of injecting either PBS (sham, n=7) or hydrogel (implant, n=7). In each compressive test, mechanical parameters were measured immediately before and after 10,000 cycles of compressive loading and following a period of hydrated recovery. The hydrogel implant was not ejected from the disc during 10,000 cycles of physiological compression testing and appeared undamaged when discs were bisected following all mechanical tests. For sham samples, creep during cyclic loading increased (+15%) from creep during nucleotomy testing, while for implant samples creep strain decreased (-3%) toward normal. There was no difference in compressive modulus or compressive strains between implant and sham samples. These findings demonstrate that the implant integrates sufficiently with the disc tissue to prevent expulsion over 10,000 cycles of compressive loading and preserves disc creep within human L5-S1 discs. This and previous studies provide a solid foundation for continuing to evaluate the efficacy of the hydrogel implant.
    Journal of Biomechanical Engineering 05/2015; DOI:10.1115/1.4030530 · 1.75 Impact Factor
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    ABSTRACT: Intervertebral disc degeneration is implicated as a major cause of low back pain. There is a pressing need for new regenerative therapies for disc degeneration that restore native tissue structure and mechanical function. To that end we investigated the therapeutic potential of an injectable, triple interpenetrating network hydrogel comprised of dextran, chitosan and teleostean, for functional regeneration of the nucleus pulposus of the intervertebral disc in a series of biomechanical, cytotoxicity and tissue engineering studies. Biomechanical properties were evaluated as a function of gelation time, with the hydrogel reaching ~90% of steady-state aggregate modulus within 10 hours. Hydrogel mechanical properties evaluated in confined and unconfined compression were comparable to native human NP properties. To confirm containment within the disc under physiological loading, toluidine blue labeled hydrogel was injected into human cadaveric spine segments after creation of a nucleotomy defect, and the segments were subjected to 10,000 cycles of loading. Gross analysis demonstrated no implant extrusion, and further, that the hydrogel interdigitated well with native NP. Constructs were next surface-seeded with NP cells and cultured for 14 days, confirming lack of hydrogel cytotoxicity, with the hydrogel maintaining NP cell viability and promoting proliferation. Next, to evaluate the potential of the hydrogel to support cell-mediated matrix production, constructs were seeded with mesenchymal stem cells (MSCs) and cultured under pro-chondrogenic conditions for up to 42 days. Importantly, the hydrogel maintained MSC viability and promoted proliferation, as evidenced by increasing DNA content with culture duration. MSCs differentiated along a chondrogenic lineage, evidenced by up-regulation of aggrecan and collagen II mRNA, and increased GAG and collagen content, and mechanical properties with increasing culture duration. Collectively, these results establish the therapeutic potential of this novel hydrogel for functional regeneration of the NP. Future work will confirm the ability of this hydrogel to normalize the mechanical stability of cadaveric human motion segments, and advance the material towards human translation using preclinical large animal models.
    Tissue Engineering Part A 01/2014; DOI:10.1089/ten.TEA.2013.0516 · 4.64 Impact Factor
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    ABSTRACT: BACKGROUND: Pathologic analysis of deep tissue obtained during debridement of venous ulcers is often unnoticed in its importance. We previously reported pathologic findings on 139 patients with venous ulcers. The objective of this study was to correlate the pathologic findings in venous ulcers with wound healing to establish a negative margin for debridement. STUDY DESIGN: Consecutive patients with a lower extremity venous ulcer present for at least 4 weeks, presenting to a single wound healing center, were included. Wounds underwent aggressive surgical debridement beyond the subcutaneous level until judged to have a viable base. Specimens were scored based on cellularity, vascularity, collagen composition, inflammation, and dense fibrosis, with a highest possible score of 13. Healing was the primary outcome for analysis. RESULTS: Of the 26 patients who met inclusion criteria, only 50% of them (13 patients) with a total of 18 venous ulcers underwent surgical debridement available for pathologic analysis. Mean ulcer area was 34.7 cm(2) at initial presentation, and 89% of patients had a continuous positive healing curve as measured by decreasing wound area (from 34.7 cm(2) to 14.3 cm(2)). However, specimens with dense fibrosis, decreased cellularity, mature collagen, and pathology score less than 10 were predominantly nonhealing ulcers. CONCLUSIONS: Presence of dense fibrosis and high levels of mature collagen in deep tissue specimens are significant correlative factors in nonhealing of venous ulcers. We recommend deep debridement on all venous ulcers that are refractory to healing until the level of absence of dense fibrosis and mature collagen is reached to promote venous ulcer healing.
    Journal of the American College of Surgeons 09/2012; 215(6). DOI:10.1016/j.jamcollsurg.2012.08.008 · 4.45 Impact Factor
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    ABSTRACT: Investigation of injectable nucleus pulposus (NP) implant. To assess the ability of a recently developed injectable hydrogel implant to restore nondegenerative disc mechanics through support of NP functional mechanics. Although surgical intervention for low back pain is effective for some patients, treated discs undergo altered biomechanics and adjacent levels are at increased risk for accelerated degeneration. One potential treatment as an alternative to surgery for degenerated disc includes the percutaneous delivery of agents to support NP functional mechanics. The implants are delivered in a minimally invasive fashion, potentially on an outpatient basis, and do not preclude later surgical options. One of the challenges in designing such implants includes the need to match key NP mechanical behavior and mimic the role of native nondegenerate NP in spinal motion. The oxidized hyaluronic acid gelatin implant material was prepared. In vitro mechanical testing was performed in mature ovine bone-disc-bone units in 3 stages: intact, discectomy, and implantation versus sham. Tested samples were cut axially for qualitative structural observations. Discectomy increased axial range of motion (ROM) significantly compared with intact. Hydrogel implantation reduced ROM 17% (P < 0.05) compared with discectomy and returned ROM to intact levels (ROM intact 0.71 mm, discectomy 0.87 mm, postimplantation 0.72 mm). Although ROM for the hydrogel implant group was statistically unchanged compared with the intact disc, ROM for sham discs, which received a discectomy and no implant, was significantly increased compared with intact. The compression and tension stiffness were decreased with discectomy and remained unchanged for both implant and sham groups as expected because the annulus fibrosus was not repaired. Gross morphology images confirmed no ejection of NP implant. An injectable implant that mimics nondegenerate NP has the potential to return motion segment ROM to normal subsequent to injury.
    Spine 05/2012; 37(18):E1099-105. DOI:10.1097/BRS.0b013e31825cdfb7 · 2.45 Impact Factor
  • Huijuan Liao, Irena Pastar, Weiliam Chen
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    ABSTRACT: Utilizing a three-dimensional in vitro glycated collagen model, we evaluated the therapeutic effects of a peroxisome proliferator-activated receptor-γ ligand, rosiglitazone, and its potential as a topical treatment of diabetic chronic wounds. Rosiglitazone induced fibroblast migration, α-smooth muscle actin production, and transformation into myofibroblasts in the presence of advanced glycation end products. Both transforming growth factor β and peroxisome proliferator-activated receptor-γ expression were induced, while the receptor for advanced glycation end products was suppressed. Lastly, the reduced activities of matrix metalloproteinase-2 and matrix metalloproteinases-9 in the carboxymethyllysine-modified collagen matrices by rosiglitazone increases extracellular matrix deposition. Our findings identify rosiglitazone as a candidate for localized topical treatment of diabetic chronic wounds.
    Wound Repair and Regeneration 05/2012; 20(3):435-43. DOI:10.1111/j.1524-475X.2012.00795.x · 2.77 Impact Factor
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    ABSTRACT: Diabetic foot ulcers (DFUs) are a significant and rapidly growing complication of diabetes and its effects on wound healing. Over half of diabetic patients who develop a single ulcer will subsequently develop another ulcer of which the majority will become chronic non-healing ulcers. One-third will progress to lower extremity amputation. Over the past decade, the outcomes for patients with DFUs ulcers have not improved, despite advances in wound care. Successful treatment of diabetic foot ulcers is hindered by the lack of targeted therapy that hones in on the healing processes dysregulated by diabetes. Stem cells are a promising treatment for DFUs as they are capable of targeting, as well as bypassing, the underlying abnormal healing mechanisms and deranged cell signaling in diabetic wounds and promote healing. This review will focus on existing stem cell technologies and their application in the treatment of DFUs.
    Diabetes research and clinical practice 12/2011; 96(1):1-9. DOI:10.1016/j.diabres.2011.10.032 · 2.54 Impact Factor
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    ABSTRACT: Fibroblasts and macrophages are the two major types of cells responding to implanted biomaterials. They play crucial roles in inflammatory responses, host-material interactions and tissue remodeling. However, the synergistic interactions of these two cell types with biomaterials are not fully understood. In this investigation, an in vitro fibroblast/macrophage co-culture system was utilized to examine the biocompatibility and the potential to induce inflammatory responses of an electrospun Dextran/PLGA scaffold. The scaffold did not affect the morphologies, attachments, proliferations and viabilities of both the fibroblasts and macrophages, cultured separately or together. Moreover, it only activated a small subset of the macrophages implicating a low potential to induce either severe acute or chronic inflammatory response. Additionally, fibroblasts played a role in prolonging macrophage activation in the presence of the scaffolds. Using antibody arrays, IL-10, SDF-1, MIP-1 gamma and RANTES were found to be up-regulated when the cells were incubated with the scaffolds. The results of subdermal implantation of the Dextran/PLGA scaffolds confirmed its biocompatibility and low inflammatory potential.
    Biomedical Materials 12/2011; 6(6):065002. DOI:10.1088/1748-6041/6/6/065002 · 2.92 Impact Factor
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    ABSTRACT: Hydroxyurea (HU) has been shown to induce a variety of cutaneous adverse reactions, including severe leg ulcers. This report shows a successful treatment of a HU-induced chronic wound associated with squamous cell carcinomas (SCC). A 62-year-old patient affected with polycythemia vera and treated with HU for 10 years, presented with a non healing ulcer on a left heel. The patient gave a history of suffering from the wound for over 2 years. Biopsy showed evidence of invasive SCC. The patient underwent Mohs surgery and a greater saphenous vein ablation for polycythemia vera-associated vascular complications. The wound consistently decreased in size following successive debridements and coverage with human skin equivalent. The wound healed completely after a 6-month period. A multidisciplinary team approach to the treatment proved to be effective resulting in healing of this multifactorial chronic ulcer.
    International Wound Journal 11/2011; 9(3):324-9. DOI:10.1111/j.1742-481X.2011.00887.x · 2.02 Impact Factor
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    ABSTRACT: The objective of the study was to inform wound care practitioners of mesenchymal stem cell application for nonhealing wounds. Recent advances in delivery systems are also discussed in order to highlight potential improvements toward clinical application of stem cell therapy for chronic wounds. MEDLINE and PubMed Central were searched for scientific studies regarding the use of mesenchymal stem cells and delivery systems in wound healing. Preclinical studies using stem cells as therapeutic modality for chronic wounds were selected for this review. Information on study design, sample size and characteristics, stem cell source, type of delivery systems, and rate and time of wound closure was abstracted. Application of mesenchymal stem cells improved wound healing in experimental and clinical settings. Advances in stem cell therapy and delivery vehicles offer promising alternatives to current limited therapeutic modalities for chronic wounds. Stem cell therapy has recently emerged as a promising therapeutic strategy for nonhealing wounds. Further research is needed to evaluate the relationship between the various delivery systems and stem cells in order to maximize their therapeutic effects. Development of novel delivery vehicles for stem cells can open new opportunities for more effective cell therapy of chronic wounds.
    Advances in skin & wound care 11/2011; 24(11):524-32; quiz 533-4. DOI:10.1097/01.ASW.0000407648.89961.a6 · 1.63 Impact Factor
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    ABSTRACT: A microfluidic emulsification method for producing monodispersed microgels from a triple interpenetrating network (3XN) hydrogel was reported. This 3XN system is comprised of minimally modified natural GRAS materials, partially oxidized dextran (Odex), Teleostean, and N-carboxyethyl chitosan (CEC), without the need of utilizing extraneous crosslinkers or photo-initiators, which has been proved to be a novel biodegradable and mechanically strong in-situ gelable hydrogel systems. A microfluidic chip was specifically designed to produce microgels from the 3XN hydrogel system. The study shows that microfluidic emulsification method could yield microgels with better size and morphology than the conventional in-emulsion-crosslinking method, and the size of microgels could be modulated by simply adjusting the flow rates of the oil and/or the individual precursor fluids. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
    Journal of Applied Polymer Science 09/2011; 121(5):3093 - 3100. DOI:10.1002/app.34001 · 1.64 Impact Factor
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    Hanwei Zhang, Aisha Qadeer, Weiliam Chen
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    ABSTRACT: In situ gelable interpenetrating double-network hydrogels composed of thiolated chitosan (Chitosan-NAC) and oxidized dextran (Odex), completely devoid of potentially cytotoxic small molecule cross-linkers and that do not require complex maneuvers or catalysis, have been formulated. The interpenetrating network structure is created by Schiff base formations and disulfide bond inter-cross-linkings through exploiting the disparity of their reaction times. Compared with the autogelable thiolated chitosan hydrogels that typically require a relatively long time span for gelation to occur, the Odex/Chitosan-NAC composition solidifies rapidly and forms a well-developed 3D network in a short time span. Compared with typical hydrogels derived from natural materials, the Odex/Chitosan-NAC hydrogels are mechanically strong and resist degradation. The cytotoxicity potential of the hydrogels was determined by an in vitro viability assay using fibroblast as a model cell, and the results reveal that the hydrogels are noncytotoxic. In parallel, in vivo results from subdermal implantation in mice models demonstrate that this hydrogel is not only highly resistant to degradation but also induces very mild tissue response.
    Biomacromolecules 03/2011; 12(5):1428-37. DOI:10.1021/bm101192b · 5.79 Impact Factor
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    ABSTRACT: An in situ gelable and biodegradable triple-interpenetrating network (3XN) hydrogel, completely devoid of potentially cytotoxic extraneous small molecule crosslinkers, is formulated from partially oxidized dextran (Odex), teleostean and N-carboxyethyl chitosan (CEC). Both the rheological profile and mechanical strength of the 3XN hydrogel approximate the combined characteristics of the three individual hydrogels composed of the binary partial formulations (i.e., Odex/CEC, Odex/teleostean, and CEC/teleostean). The 3XN hydrogel is considerably more resistant to fibroblast-mediated degradation compared to each partial formulation in cell culture models; this is attributable to the interpenetrating triple-network structure. The presence of teleostean in the 3XN hydrogel imparts cell affinity, constituting an environment amenable to fibroblast growth. in vivo subdermal injection into mouse model shows that the 3XN hydrogel does not induce extensive inflammatory response nor is there any evidence of tissue necrosis, further confirming the non-cytotoxicity of the hydrogel and its degradation byproducts. Importantly, the capability of the 3XN hydrogel to serve as a sustained drug delivery vehicle is confirmed using rosiglitazone as a model drug. The presence of rosiglitazone profoundly changes the cell/tissue interactions with the subdermally injected 3XN hydrogel. Rosiglitazone suppresses both the inflammatory response and tissue repair in a dose-dependent manner and considerably moderated the hydrogel degradation.
    Biomaterials 10/2010; 32(3):890-8. DOI:10.1016/j.biomaterials.2010.09.053 · 8.31 Impact Factor
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    Qiong Zeng, Weiliam Chen
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    ABSTRACT: Tissues/cells-mediated biodegradable material degradation is epitomized by the constantly changing tissues/cell-implant interface, implicating the constant adaptation of the tissues/cells. Macrophages and fibroblasts are multi-functional cells highly involved in the interactions; the two cell types modulates the behaviors of each other, but their combinatorial functional behavior in the presence of interactive bioactive wound dressings has not been adequately examined. The activity is further complicated by the implantation of biodegradable materials, such as hydrogels commonly utilized as wound dressings, in a pathological environment and this is exemplified by the macrophages with a diabetic pathology producing an alternative cytokine profile which is implicated in wound healing delay. In this study, an in situ gelable formable/conformable hydrogel formulated from modified alginate and marine gelatin was used as a model biodegradable interactive wound dressing to elucidate the combinatorial behavior of macrophages/fibroblasts derived from both normal and diabetic hosts. Cell proliferation, migration and distribution were first characterized; this was followed by simultaneous quantitative detection of 40 inflammatory cytokines and chemokines by a protein microarray. The results showed that the macrophages/fibroblasts co-culture promoted fibroblasts proliferation and migration in the presence of the hydrogel; moreover, the expressions of inflammatory cytokines and chemokines were altered when compared with the corresponding fibroblasts or macrophages monocultures. The inflammatory cytokines patterns between the normal and diabetic hosts were considerably different.
    Biomaterials 08/2010; 31(22):5772-81. DOI:10.1016/j.biomaterials.2010.04.022 · 8.31 Impact Factor
  • Hanwei Zhang, Huijuan Liao, Weiliam Chen
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    ABSTRACT: An in situ gelable glycation-resistant hydrogel has been prepared from oxidized alginate (Oalg) and gelatin. Aminoguanidine, an effective inhibitor of the glycation reaction, was first encapsulated in gelatin microspheres followed by incorporation into the hydrogel. The gelation process was monitored rheologically, and the results showed that the AMG-loaded Oalg/gelatin system solidified quickly at body temperature. Moreover, the hydrogels were highly porous, and the AMG-loaded microspheres dispersed in the hydrogels remained intact. Hydrogels' AMG loadings did not appear to change their degradation behaviors. AMG could be released from the hydrogels in a sustainable manner for a relatively short duration. Incorporation of AMG into the hydrogels resulted in imparting a glycation-resistant capability. Lastly, long-term in vitro incubation of all hydrogel formulations with fibroblasts did not reveal any cytotoxic potential.
    Journal of Biomaterials Science Polymer Edition 01/2010; 21(3):329-42. DOI:10.1163/156856209X415864 · 1.36 Impact Factor
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    ABSTRACT: Creating monodispersed hydrogel microparticles is advantageous for drug delivery applications. We explore microfluidic flow focusing as a method for generating such particles. Our hydrogel has a unique composition that makes it biodegradable and mechanically strong. We designed and manufactured a polymer microfluidic chip that mixes three viscous precursor solutions and generates a steady stream of microparticles from that solution. We found that microfluidic flow focusing produce particle with a coefficient of variance around 9%; this was a four times improvement over traditional methods.
    ASME 2010 8th International Conference on Nanochannels, Microchannels, and Minichannels collocated with 3rd Joint US-European Fluids Engineering Summer Meeting; 01/2010
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    ABSTRACT: Treatment of cerebral aneurysms by endovascular deployment of liquid embolic agents has been proposed as an alternative strategy to conventional coiling, and new materials are being developed for embolization. In this study, the authors used a single-injection, biocompatible, biodegradable and pH-responsive acrylated chitosan (aCHN) with conjugated vascular endothelial growth factor (rhVEGF) in a rat aneurysm model. The efficacy of the aCHN formulation with rhVEGF was tested using a common carotid artery occlusion model in rats, and the extent of embolization was evaluated using quantitative, qualitative, and histopathological techniques after 14 days of implantation. The mean occlusion was significantly greater for the rhVEGF/aCHN-treated group (96.8 +/- 3.0%) than for the group receiving aCHN (74.7 +/- 5.6%) (p < 0.01). Through qualitative evaluation, intimal and medial proliferation were significantly greater with rhVEGF/aCHN than with aCHN and controls (p < 0.001). Degradation of the aCHN filler was monitored in concert with the production of extracellular matrix components. Macrophages migrated in and proliferated inside the occluded carotid artery lumens were identified by histological and immunostainings. Results showed resorption of chitosan with concurrent development of collagen and elastin into the vessel lumen, suggesting clot maturation into fibrosis. Chitosan with a bioactive agent such as rhVEGF showed excellent results in occluding aneurysms in a rat model.
    Journal of Neurosurgery 08/2009; 112(3):658-65. DOI:10.3171/2009.1.JNS08411 · 3.15 Impact Factor
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    ABSTRACT: Closure of diabetic dermal chronic wounds remains a clinical challenge. Implant-assisted healing is emerging as a potential class of therapy for dermal wound closure; this advancement has not been paralleled by the development in complementary diagnostic techniques to objectively monitor the wound-healing process in conjunction with assessing/monitoring of implant efficacy. Biopsies provide the most objective morphological assessments of wound healing; however, they not only perpetuate the wound presence but also increase the risk of infection. A noninvasive and high-resolution imaging technique is highly desirable to provide objective longitudinal diagnosis of implant-assisted wound healing. We investigated the feasibility of deploying optical coherence tomography (OCT) for noninvasive monitoring of the healing of full-thickness excisional dermal wounds implanted with a novel in situ gelable hydrogel composed of N-carboxyethyl chitosan, oxidized dextran, and hyaluronan, in both normal and db/db mice. The results showed that OCT was able to differentiate the morphological differences (e.g., thickness of dermis) between normal and diabetic mice as validated by their corresponding histological evaluations (p < 0.05). OCT could detect essential morphological changes during wound healing, including re-epithelization, inflammatory response, and granulation tissue formation as well as impaired wound repair in diabetic mice. Importantly, by tracking specific morphological changes in hydrogel-assisted wound healing (e.g., implants' degradation and resorption, cell-mediated hydrogel degradation, and accelerated re-epithelization), OCT could also be deployed to monitor and evaluate the transformation of implanted biomaterials, thus holding the promise for noninvasive and objective monitoring of wound healing longitudinally and for objective efficacy assessment of implantable therapeutics in tissue engineering.
    Tissue Engineering Part C Methods 07/2009; 16(2):237-47. DOI:10.1089/ten.TEC.2009.0152 · 4.64 Impact Factor
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    Huijuan Liao, Julia Zakhaleva, Weiliam Chen
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    ABSTRACT: Dermal accumulation of advanced glycation end products (AGEs) has increasingly been implicated as the underlying cause of delayed diabetic wound healing. Devising an in vitro model to adequately mimic glycated tissues will facilitate investigation into the mechanism of glycation in conjunction with exploration of new approaches or improvement of current therapies for treating diabetic chronic wounds. Collagen matrices were artificially glycated and the presence of AGEs was demonstrated by immunostaining. Both the mechanical properties of the collagen matrices and their interactions with fibroblasts (morphology, attachment, proliferation, and migration) were altered after glycation, moreover, there was evidence of impairment on extracellular matrix (ECM) remodeling as well as inhibition of cell-induced material contraction. The actin cytoskeletons of the fibroblasts residing in the glycated collagen matrices were reorganized. In vivo mice full-thickness dermal wound models implanted with glycated collagen matrices showed delayed wound healing response. Thus, the glycated collagen matrix is an adequate in vitro model to mimic glycated tissues and could serve as a facile experimental tool to investigate the mechanism of glycation in conjunction with exploration of new approaches or improvement of current therapies for treating diabetic wounds.
    Biomaterials 02/2009; 30(9):1689-96. DOI:10.1016/j.biomaterials.2008.11.038 · 8.31 Impact Factor
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    ABSTRACT: One mechanism that contributes to cerebral vasospasm is the impairment of potassium channels in vascular smooth muscles. Adenosine triphosphate-sensitive potassium channel openers (PCOs) appear to be particularly effective for dilating cerebral arteries in experimental models of subarachnoid hemorrhage (SAH). A mode of safe administration that provides timed release of PCO drugs is still a subject of investigation. The authors tested the efficacy of locally delivered intrathecal cromakalim, a PCO, incorporated into a controlled-release system to prevent cerebral vasospasm in a rat model of SAH. Cromakalim was coupled to a viscous carrier, hyaluronan, 15% by weight. In vitro release kinetics studies showed a steady release of cromakalim over days. Fifty adult male Sprague-Dawley rats weighing 350-400 g each were divided into 10 groups and treated with various doses of cromakalim or cromakalim/hyaluronan in a rat double SAH model. Treatment was started 30 minutes after the second SAH induction. Animals were killed 3 days after treatment, and the basilar arteries were processed for morphometric measurements and histological analysis. Controlled release of cromakalim from the cromakalim/hyaluronan implant at a dose of 0.055 mg/kg significantly increased lumen patency in a dose-dependent manner up to 94 +/- 8% (mean +/- standard error of the mean) of the basilar arteries of the sham group compared with the empty polymer group (p = 0.006). Results in the empty polymer group were not different from those in the SAH-only group, with a lumen patency of 65 +/- 12%. Lumen patencies of the cromakalim-only groups did not differ in statistical significance at low (64 +/- 9%) or high (66 +/- 7%) doses compared to the SAH-only group. Treatment of SAH with a controlled-release cromakalim/hyaluronan implant prevented experimental cerebral vasospasm in this rat double hemorrhage model; this inhibition was dose-dependent. The authors' results confirm that sustained delivery of cromakalim perivascularly to cerebral vessels could be an effective therapeutic strategy in the treatment of cerebral vasospasm after SAH.
    Journal of Neurosurgery 02/2009; 110(5):1015-20. DOI:10.3171/2008.8.JNS08202 · 3.23 Impact Factor
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    ABSTRACT: Microspheres formulated from blending poly(lactide-co-glycolide) (PLGA) and poly(ethylene glycol)-grafted-chitosan (PEG-g-CHN), using a modified in-emulsion-solvent-evaporation method, were investigated for the delivery of protein. A model protein, bovine serum albumin (BSA), was incorporated into the PLGA/PEG-g-CHN microspheres and both initial burst and release kinetics could be modulated by varying the PEG-g-CHN content. Basic fibroblast growth factor (bFGF) was formulated into the microspheres containing 5% PEG-g-CHN and the bFGF contents in the releasates were determined by a receptor-based ELISA with their in vitro bioactivities validated by fibroblast cell culture. The in vivo effect of the bFGF microspheres formulation was evaluated in a hamster cheek pouch model using a 7 day exposure (e.g., before significant vascular remodeling was expected). Using intravital microscopy, the tissue showed no evidence of inflammation with any formulation; deliberate activation of a preconditioning response linked to inflammation was attenuated by BSA microspheres alone. Vasoactive responses (receptor-dependant and independent constriction and dilation) linked to nitric oxide were attenuated, and constriction to endothelin was enhanced in bFGF and not BSA containing microspheres. PLGA/PEG-g-CHN blended microspheres were also demonstrated to be non-inflammatory and non-thrombogenic in vivo by observing the vascular changes in the cheek pouch. In conclusion, the addition of PEG-g-CHN to PLGA microspheres can serve as a sustained delivery vehicle for bFGF and the released protein provides vasoactive changes consistent with chronic bFGF exposure.
    Journal of Biomaterials Science Polymer Edition 02/2009; 20(7-8):903-22. DOI:10.1163/156856209X444330 · 1.36 Impact Factor

Publication Stats

1k Citations
188.65 Total Impact Points


  • 2011–2014
    • CUNY Graduate Center
      New York, New York, United States
    • Tufts University
      • Department of Medicine
      Medford, MA, United States
  • 2011–2012
    • NYU Langone Medical Center
      • Department of Surgery
      New York, New York, United States
  • 2004–2010
    • Stony Brook University
      • Department of Biomedical Engineering
      Stony Brook, New York, United States
  • 2004–2008
    • State University of New York
      New York City, New York, United States