7 research outputs found
Hemocompatibility of Silicon-Based Substrates for Biomedical Implant Applications
Silicon membranes with highly uniform nanopore sizes fabricated using microelectromechanical systems (MEMS) technology allow for the development of miniaturized implants such as those needed for renal replacement therapies. However, the blood compatibility of silicon has thus far been an unresolved issue in the use of these substrates in implantable biomedical devices. We report the results of hemocompatibility studies using bare silicon, polysilicon, and modified silicon substrates. The surface modifications tested have been shown to reduce protein and/or platelet adhesion, thus potentially improving biocompatibility of silicon. Hemocompatibility was evaluated under four categories—coagulation (thrombin–antithrombin complex, TAT generation), complement activation (complement protein, C3a production), platelet activation (P-selectin, CD62P expression), and platelet adhesion. Our tests revealed that all silicon substrates display low coagulation and complement activation, comparable to that of Teflon and stainless steel, two materials commonly used in medical implants, and significantly lower than that of diethylaminoethyl (DEAE) cellulose, a polymer used in dialysis membranes. Unmodified silicon and polysilicon showed significant platelet attachment; however, the surface modifications on silicon reduced platelet adhesion and activation to levels comparable to that on Teflon. These results suggest that surface-modified silicon substrates are viable for the development of miniaturized renal replacement systems
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Effect of polymer conjugation and nanotopography on implant compatibility and wound healing
This dissertation focuses on two aspects that present challenges for a broad range of implantable devices and transplants - blood compatibility and wound healing properties of biomaterials. In the first chapter, we examined the hemocompatibility of surface modified silicon substrates used in renal replacement devices. Our reports showed that the polymer conjugated silicon samples reduced platelet attachment and activation to levels comparable to that on Teflon, a material commonly used in medical implant devices. Our findings suggest that surface modified silicon substrates could be used to develop miniaturized implants for renal replacement therapies. In the second chapter, we investigated how collagen nanotopography affects wound healing in the cornea. The presence of nanopatterned collagen fibrils was shown to promote the appearance of the healthy keratocyte phenotype and attenuate the fibrotic myofibroblast phenotype. In addition, collagen nanotopography also had an effect on matrix synthesis. These results have significant implications for the design of tissue engineered corneal substitutes and for promoting regenerative wound healing in the cornea.In the third chapter, we focused on wound healing in the skin, particularly in the case of keloid scars. Keloids are locally aggressive dermal scars formed as a result of abnormal wound healing. They are characterized by excessive fibroblast proliferation and matrix production. An effective treatment for keloids is yet to be established due to a high rate of recurrence. Our results showed that collagen fibril alignment reduced cell proliferation and matrix synthesis in fibroblasts derived from keloid, scar and healthy dermal tissue. This data suggests that aligned collagen fibrils could be used to develop dermal patches that reduce the recurrence of keloids and aid in the design of an effective therapy for keloid management. The recurring theme in both the cornea and keloid studies is that matrix architecture could be used to effectively manipulate cell response to direct regenerative wound healing. Collectively our findings show that physical cues such as matrix topography could be used to improve the anti-fibrotic properties of biomaterials and aid in the design of tissue engineered implants for various clinical applications