Silicone grafted bioactive peptides and their applications

Silanization Strategies for Tailoring Peptide Functionalization on Silicon Surfaces: Implications for Enhancing Stem Cell Adhesion

Biomaterial surface engineering and the integration of cell-adhesive ligands are crucial in biological research and biotechnological applications. The interplay between cells and their microenvironment, influenced by chemical and physical cues, impacts cellular behavior. Surface modification of biomaterials profoundly affects cellular responses, especially at the cell-surface interface. This work focuses on enhancing cellular activities through material manipulation, emphasizing silanization for further functionalization with bioactive molecules such as RGD peptides to improve cell adhesion. The grafting of three distinct silanes onto silicon wafers using both spin coating and immersion methods was investigated. This study sheds light on the effects of different alkyl chain lengths and protecting groups on cellular behavior, providing valuable insights into optimizing silane-based self-assembled monolayers (SAMs) before peptide or protein grafting for the first time. Specifically, it challenges the common use of APTES molecules in this context. These findings advance our understanding of surface modification strategies, paving the way for tailoring biomaterial surfaces to modulate the cellular behavior for diverse biotechnological applications.

Neural grafts containing exosomes derived from Schwann cell-like cells promote peripheral nerve regeneration in rats

Background

Schwann cell-like cells (SCLCs), differentiated from mesenchymal stem cells, have shown promising outcomes in the treatment of peripheral nerve injuries in preclinical studies. However, certain clinical obstacles limit their application. Hence, the primary aim of this study was to investigate the role of exosomes derived from SCLCs (SCLCs-exo) in peripheral nerve regeneration.

Methods

SCLCs were differentiated from human amniotic mesenchymal stem cells (hAMSCs) in vitro and validated by immunofluorescence, real-time quantitative PCR and western blot analysis. Exosomes derived from hAMSCs (hAMSCs-exo) and SCLCs were isolated by ultracentrifugation and validated by nanoparticle tracking analysis, WB analysis and electron microscopy. A prefabricated nerve graft was used to deliver hAMSCs-exo or SCLCs-exo in an injured sciatic nerve rat model. The effects of hAMSCs-exo or SCLCs-exo on rat peripheral nerve injury (PNI) regeneration were determined based on the recovery of neurological function and histomorphometric variation. The effects of hAMSCs-exo or SCLCs-exo on Schwann cells were also determined via cell proliferation and migration assessment.

Results

SCLCs significantly expressed the Schwann cell markers glial fibrillary acidic protein and S100. Compared to hAMSCs-exo, SCLCs-exo significantly enhanced motor function recovery, attenuated gastrocnemius muscle atrophy and facilitated axonal regrowth, myelin formation and angiogenesis in the rat model. Furthermore, hAMSCs-exo and SCLCs-exo were efficiently absorbed by Schwann cells. However, compared to hAMSCs-exo, SCLCs-exo significantly promoted the proliferation and migration of Schwann cells. SCLCs-exo also significantly upregulated the expression of a glial cell-derived neurotrophic factor, myelin positive regulators (SRY-box transcription factor 10, early growth response protein 2 and organic cation/carnitine transporter 6) and myelin proteins (myelin basic protein and myelin protein zero) in Schwann cells.

Conclusions

These findings suggest that SCLCs-exo can more efficiently promote PNI regeneration than hAMSCs-exo and are a potentially novel therapeutic approach for treating PNI.

Repair of peripheral nerve defects by nerve grafts incorporated with extracellular vesicles from skin-derived precursor Schwann cells

Our previous studies have shown that extracellular vesicles from skin-derived precursor Schwann cells (SKP-SC-EVs) promote neurite outgrowth of sensory and motor neurons in vitro. This study was aimed at generating an artificial nerve graft incorporated with SKP-SC-EVs to examine in vivo effects of SKP-SC-EVs on peripheral nerve regeneration. Here SKP-SC-EVs were isolated and then identified by morphological observation and phenotypic marker expression. Following co-culture with SCs or motoneurons, SKP-SC-EVs were internalized, showing the capability to enhance SC viability or motoneuron neurite outgrowth. In vitro, SKP-SC-EVs released from Matrigel could maintain cellular uptake property and neural activity. Nerve grafts were developed by incorporating Matrigel-encapsulated SKP-SC-EVs into silicone conduits. Functional evaluation, histological investigation, and morphometric analysis were performed to compare the nerve regenerative outcome after bridging the 10-mm long sciatic nerve defect in rats with our developed nerve grafts, silicone conduits (filled with vehicle), and autografts respectively. Our developed nerve grafts significantly accelerated the recovery of motor, sensory, and electrophysiological functions of rats, facilitated outgrowth and myelination of regenerated axons, and alleviated denervation-induced atrophy of target muscles. Collectively, our findings suggested that incorporation of SKP-SC-EVs into nerve grafts might represent a promising paradigm for peripheral nerve injury repair. STATEMENT OF SIGNIFICANCE: Nerve grafts have been progressively developed to meet the increasing requirements for peripheral nerve injury repair. Here we reported a design of nerve grafts featured by incorporation of Matrigel-encapsulated extracellular vesicles from skin-derived precursor Schwann cells (SKP-SC-EVs), because SKP-SC-EVs were found to possess in vitro neural activity, thus raising the possibility of cell-free therapy. Our developed nerve grafts yielded the satisfactory outcome of nerve grafting in rats with a 10-mm long sciatic nerve defect, as evaluated by functional and morphological assessments. The promoting effects of SKP-SC-EVs-incorporating nerve grafts on peripheral nerve regeneration might benefit from in vivo biological cues afforded by SKP-SC-EVs, which had been released from Matrigel and then internalized by residual neural cells in sciatic nerve stumps.

What affects the biocompatibility of polymers?

In recent decades synthetic polymers have gained increasing popularity, and nowadays they are an integral part of people's daily lives. In addition, owing to their competitive advantage and being susceptible to modification, polymers have stimulated the fast development of innovative technologies in many areas of science. Biopolymers are of particular interest in various branches of medicine, such as implantology of bones, cartilage and skin tissues as well as blood vessels. Biomaterials with such specific applications must have appropriate mechanical and strength characteristics and above all they must be compatible with the surrounding tissues, human blood and its components, i.e. exhibit high hemo- and biocompatibility, low or no thrombo- and carcinogenicity, foreign body response (host response), appropriate osteoconduction, osteoinduction and mineralization. For biocompatibility improvement many surface treatment techniques have been utilized leading to fabricate the polymer biomaterials of required properties, also at nanoscale. This review paper discusses the most important physicochemical and biological factors that affect the biocompatibility, thus the reaction of the living organism after insertion of the polymer-based biomaterials, i.e. surface modification and/or degradation, surface composition (functional groups and charge), size and shapes, hydrophilic-hydrophobic character, wettability and surface free energy, topography (roughness, stiffness), crystalline and amorphous structure, nanostructure, cell adhesion and proliferation, cellular uptake. Particularly, the application of polysaccharides (chitosan, cellulose, starch) in the tissue engineering is emphasized.

Review of silicone surface modification techniques and coatings for antibacterial/antimicrobial applications to improve breast implant surfaces

Silicone implants are widely used in the medical field for plastic or reconstructive surgeries for the purpose of soft tissue issues. However, as with any implanted object, healthcare-associated infections are not completely avoidable. The material suffers from a lack of biocompatibility and is often subject to bacterial/microbial infections characterized by biofilm growth. Numerous strategies have been developed to either prevent, reduce, or fight bacterial adhesion by providing an antibacterial property. The present review summarizes the diverse approaches to deal with bacterial infections on silicone surfaces along with the different methods to activate/oxidize the surface before any surface modifications. It includes antibacterial coatings with antibiotics or nanoparticles, covalent attachment of active bacterial molecules like peptides or polymers. Regarding silicone surfaces, the activation step is essential to render the surface reactive for any further modifications using energy sources (plasma, UV, ozone) or chemicals (acid solutions, sol-gel strategies, chemical vapor deposition). Meanwhile, corresponding work on breast silicone prosthesis is discussed. The latter is currently in the line of sight for causing severe capsular contractures. Specifically, to that end, besides chemical modifications, the antibacterial effect can also be achieved by physical surface modifications by adjusting the surface roughness and topography for instance.