Abstract
BackgroundAerogels are a versatile group of nanostructured/nanoporous materials with physical and chemical properties that can be adjusted to suit the application of interest. In terms of biomedical applications, aerogels are particularly suitable for implants such as membranes, tissue growth scaffolds, and nerve regeneration and guidance inserts. The mesoporous nature of aerogels can also be used for diffusion based release of drugs that are loaded during the drying stage of the material. From the variety of aerogels polyurea crosslinked silica aerogels have the most potential for future biomedical applications and are explored here.MethodologyThis study assessed the short and long term biocompatibility of polyurea crosslinked silica aerogel implants in a Sprague-Dawley rat model. Implants were inserted at two different locations a) subcutaneously (SC), at the dorsum and b) intramuscularly (IM), between the gluteus maximus and biceps femoris of the left hind extremity. Nearby muscle and other internal organs were evaluated histologically for inflammation, tissue damage, fibrosis and movement (travel) of implant.Conclusion/SignificanceIn general polyurea crosslinked silica aerogel (PCSA) was well tolerated as a subcutaneous and an intramuscular implant in the Sprague-Dawley rat with a maximum incubation time of twenty months. In some cases a thin fibrous capsule surrounded the aerogel implant and was interpreted as a normal response to foreign material. No noticeable toxicity was found in the tissues surrounding the implants nor in distant organs. Comparison was made with control rats without any implants inserted, and animals with suture material present. No obvious or noticeable changes were sustained by the implants at either location. Careful necropsy and tissue histology showed age-related changes only. An effective sterilization technique for PCSA implants as well as staining and sectioning protocol has been established. These studies further support the notion that silica-based aerogels could be useful as biomaterials.
Highlights
Porous biocompatible materials have received particular attention in recent years for a broad range of applications
Large pore sizes restrict the use of this class of porous materials to whole cell penetration and tissue infiltration applications only, making them unsuitable for drug delivery and protein loading applications where the physical size of the entities of interest are on the order of 10 s of nanometers rather than microns [9,10]
Results presented in this study demonstrate the biocompatibility of polyurea crosslinked silica aerogel (PCSA) thereby supporting the notion that these materials could be useful for biomedical applications
Summary
Porous biocompatible materials have received particular attention in recent years for a broad range of applications. From filters and prostheses to scaffolds for tissue engineering, porous biomaterials have been under constant development and improvement for biological and biomedical applications [1,2,3,4,5,6,7]. Complications such as poor mechanical performances, batch-to-batch purity variations, and large pore sizes (mm –range) have limited the extent of use of naturally occurring biomaterials [8] even though they most closely simulate the native cellular environment. From the variety of aerogels polyurea crosslinked silica aerogels have the most potential for future biomedical applications and are explored here
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