Enhancing tissue integration and angiogenesis of a novel nanocomposite polymer using plasma surface polymerisation, an in vitro and in vivo study

Photo-crosslinked chitosan-gelatin xerogel-like coating onto "cold" plasma functionalized poly(lactic acid) film as cell culture support

This paper reports on biofunctionalisation of a poly(lactic acid) (PLA) film by surface activation through cold plasma treatment followed by coating with a chitosan-gelatin xerogel. The UV cross-linking of the xerogel precursor was simultaneously performed with the fixation onto the PLA support. This has a strong effect on surface properties, in terms of wettability, surface free energy, morphology and micromechanical features. The hydrophilic - hydrophobic character of the surface, determined by contact angle measurements, was tuned along the process, passing from moderate hydrophobic PLA to enhanced hydrophilic plasma activated surface, which favors coating adhesion, then to moderate hydrophobic chitosan-gelatin coating. The coating has a Lewis amphoteric surface, with a porous xerogel-like morphology, as revealed by scanning electron microscopy images. By riboflavin mediated UV cross-linking the chitosan-gelatin coating becomes high adhesive and with a more pronounced plasticity, as shown by AFM force-distance spectroscopy. Thus prepared surface-coated PLA supports were successfully tested for growth of dermal fibroblasts, which are known for their induction potential of chondrogenic cells, which is very important in cartilage tissue engineering.

Thermoplastic polyurethane/POSS nanohybrids: Synthesis, morphology, and biological properties

Recent studies show good osteoinductive properties of polyurethanes modified with polyhedral oligomeric silsesquioxanes (POSS). In this work, three types of POSS; propanediolisobutyl-POSS (PHI-POSS), disilanolisobutyl-POSS (DSI-POSS), and octahydroxybutyl-POSS (OCTA-POSS) were chemically incorporated into linear polyurethane based on an aliphatic isocyanate, hexamethylene diisocyanate (HDI), to obtain new nanohybrid PU-POSS materials. The full conversion of POSS was confirmed by Fourier transform infrared spectroscopy (FTIR-ATR) spectra of the model reactions with pure HDI. The materials obtained were investigated by FTIR, SEM-EDS, and DSC. The DSC studies showed the thermoplasticity of the obtained materials and apparently good recovery. 30-day immersion in SBF (simulated body fluid) revealed an increase in the rate of deposition of hydroxyapatite (HAp) for the highest POSS loadings, resulting in thick layers of hydroxyapatite (~60-40 μm), and the Ca/P ratio 1.67 (even 1.785). The structure and properties of the inorganic layer depend on the type of POSS, the number of hard segments, and those containing POSS, which can be tailored by changing the HDI/poly(tetramethylene glycol) (PTMG) ratio. Furthermore, the obtained composites revealed good biocompatibility, as confirmed by cytotoxicity tests conducted on two cell lines; normal human dermal fibroblasts (NHDF) and primary human osteoblasts (HOB). Adherent cells seeded on the tested materials showed viability even after a 48-h incubation. After this time, the population of viable, and proliferating cells exceeded 90%. Bioimaging studies have shown the fibroblast and osteoblast cells were well attached to the surface of the tested materials.

POSS and SSQ Materials in Dental Applications: Recent Advances and Future Outlooks

Recently, silsesquioxanes (SSQ) and polyhedral oligomeric silsesquioxanes (POSS) have gained much interest in the area of biomaterials, mainly due to their intrinsic properties such as biocompatibility, complete non-toxicity, the ability to self-assemble and to form a porous structure, facilitating cell proliferation, creating a superhydrophobic surface, osteoinductivity, and ability to bind hydroxyapatite. All the above has resulted in new developments in medicine. However, the application of POSS-containing materials in dentistry is still at initial stage and deserves a systematic description to ensure future development. Significant problems, such as reduction of polymerization shrinkage, water absorption, hydrolysis rate, poor adhesion and strength, unsatisfactory biocompatibility, and corrosion resistance of dental alloys, can be addressed by the design of multifunctional POSS-containing materials. Because of the presence of silsesquioxanes, it is possible to obtain smart materials that allow the stimulation of phosphates deposition and repairing of micro-cracks in dental fillings. Hybrid composites result in materials exhibiting shape memory, as well as antibacterial, self-cleaning, and self-healing properties. Moreover, introducing POSS into polymer matrix allows for materials for bone reconstruction, and wound healing. This review covers the recent developments in the field of POSS application in dental materials and gives the future perspectives within a promising field of biomedical material science and chemical engineering.

Surface Tailoring of 3D Scaffolds to Promote Osteogenic Differentiation

Customized bone scaffolds with osteogenic activities are desired for the regenerative repair of large-scale or irregularly shaped bone defects. This study developed a facile method to create osteogenic surfaces on three-dimensional (3D) printed scaffolds through coating-induced mineralization. The coating was synthesized using chemical vapor deposition of a polyelectrolyte containing oppositely charged groups. The opposite charges on the 3D scaffold played a crucial role in promoting the formation of nanoapatites without agglomeration, resulting in the retention of micro- and nanoscale pore openings needed for preosteoblasts to proliferate, differentiate, and migrate. The nanoapatite scaffold exhibited significant enhancement in osteoinductivity with a 107% increase in alkaline phosphatase expression and a 163% increase in osteocalcin activity compared to the pristine scaffold. The nanoapatite scaffold provided cues for preosteoblasts to grow along aligned features and migrate collectively. The findings of this study demonstrate the synergistic effect of oppositely charged polyelectrolytes and mineralized nanoapatites on promoting osteogenic activities on scaffold surfaces.

A Review of Woven Tracheal Stents: Materials, Structures, and Application

The repair and reconstruction of tracheal defects is a challenging clinical problem. Due to the wide choice of materials and structures, weaving technology has shown unique advantages in simulating the multilayer structure of the trachea and providing reliable performance. Currently, most woven stent-based stents focus only on the effect of materials on stent performance while ignoring the direct effect of woven process parameters on stent performance, and the advantages of weaving technology in tissue regeneration have not been fully exploited. Therefore, this review will introduce the effects of stent materials and fabric construction on the performance of tracheal stents, focusing on the effects of weaving process parameters on stent performance. We will summarize the problems faced by woven stents and possible directions of development in the hope of broadening the technical field of artificial trachea preparation.

Improving Vascularization of Biomaterials for Skin and Bone Regeneration by Surface Modification: A Narrative Review on Experimental Research

Artificial tissue substitutes are of great interest for the reconstruction of destroyed and non-functional skin or bone tissue due to its scarcity. Biomaterials used as scaffolds for tissue regeneration are non-vascularized synthetic tissues and often based on polymers, which need ingrowth of new blood vessels to ensure nutrition and metabolism. This review summarizes previous approaches and highlights advances in vascularization strategies after implantation of surface-modified biomaterials for skin and bone tissue regeneration. The efficient integration of biomaterial, bioactive coating with endogenous degradable matrix proteins, physiochemical modifications, or surface geometry changes represents promising approaches. The results show that the induction of angiogenesis in the implant site as well as the vascularization of biomaterials can be influenced by specific surface modifications. The neovascularization of a biomaterial can be supported by the application of pro-angiogenic substances as well as by biomimetic surface coatings and physical or chemical surface activations. Furthermore, it was confirmed that the geometric properties of the three-dimensional biomaterial matrix play a central role, as they guide or even enable the ingrowth of blood vessels into a biomaterial.

Modification of polyetheretherketone (PEEK) physical features to improve osteointegration

Polyetheretherketone (PEEK) has been widely applied in orthopedics because of its excellent mechanical properties, radiolucency, and biocompatibility. However, the bioinertness and poor osteointegration of PEEK have greatly limited its further application. Growing evidence proves that physical factors of implants, including their architecture, surface morphology, stiffness, and mechanical stimulation, matter as much as the composition of their surface chemistry. This review focuses on the multiple strategies for the physical modification of PEEK implants through adjusting their architecture, surface morphology, and stiffness. Many research findings show that transforming the architecture and incorporating reinforcing fillers into PEEK can affect both its mechanical strength and cellular responses. Modified PEEK surfaces at the macro scale and micro/nano scale have positive effects on cell-substrate interactions. More investigations are necessary to reach consensus on the optimal design of PEEK implants and to explore the efficiency of various functional implant surfaces. Soft-tissue integration has been ignored, though evidence shows that physical modifications also improve the adhesion of soft tissue. In the future, ideal PEEK implants should have a desirable topological structure with better surface hydrophilicity and optimum surface chemistry.

Recent Advances in Polyurethane/POSS Hybrids for Biomedical Applications

Advanced organic-inorganic materials-composites, nanocomposites, and hybrids with various compositions offer unique properties required for biomedical applications. One of the most promising inorganic (nano)additives are polyhedral oligomeric silsesquioxanes (POSS); their biocompatibility, non-toxicity, and phase separation ability that modifies the material porosity are fundamental properties required in modern biomedical applications. When incorporated, chemically or physically, into polyurethane matrices, they substantially change polymer properties, including mechanical properties, surface characteristics, and bioactivity. Hence, this review is dedicated to POSS-PU composites that have recently been developed for applications in the biomedical field. First, different modes of POSS incorporation into PU structure have been presented, then recent developments of PU/POSS hybrids as bio-active composites for scaffolds, cardiovascular stents, valves, and membranes, as well as in bio-imaging and cancer treatment, have been described. Finally, characterization and methods of modification routes of polyurethane-based materials with silsesquioxanes were presented.

Construction of a hierarchical micro & nanoporous surface for loading genistein on the composite of polyetheretherketone/tantalum pentoxide possessing antibacterial activity and accelerated osteointegration

Nanoporous tantalum pentoxide (NTP) particles with a pore size of about 10 nm were synthesized and blended with polyetheretherketone (PEEK) to fabricate a PEEK/NTP composite (PN). Subsequently, PN was treated by concentrated sulfuric acid to create a microporous surface (pore size of around 2 μm) on sulfonated PN (SPN), which formed a hierarchical micro & nanoporous surface. Compared with PN, the porous surface of SPN exhibited higher roughness, hydrophilicity, and surface energy. In addition, genistein (GT) was loaded into the porous surface of SPN (SPNG), which showed high GT loading capacity and sustained release of GT into phosphate buffered saline (PBS). Moreover, SPNG revealed excellent antibacterial activity, which inhibited bacterial (E. coli and S. aureus) growth in vitro due to the synergistic effects of both sulfonic acid (SO3H) groups and the sustained release of GT. Compared with PN, SPN significantly improved the adhesion, proliferation, and osteogenic differentiation of bone mesenchymal stem cells in vitro. Moreover, compared with SPN, SPNG further enhances the cell responses. Compared with PN, SPN remarkably improved bone formation and osteointegration in vivo. Furthermore, compared with SPN, SPNG further enhanced the osteointegration. In short, SPNG with a micro & nanoporous surface, SO3H groups, and the sustained release of GT exhibited antibacterial activity and accelerated osteointegration, which would have tremendous potential as drug-loaded implants for bone substitute.

A dynamic remodeling bio-mimic extracellular matrix to reduce thrombotic and inflammatory complications of vascular implants

Thrombotic and inflammatory complications induced by vascular implants remain a challenge to treat cardiovascular disease due to the lack of self-adaption and functional integrity of implants. Inspired by the dynamic remodeling of the extracellular matrix (ECM), we constructed a bio-mimic ECM with a dual-layer nano-architecture on the implant surface to render the surface adaptive to inflammatory stimuli and remodelable possessing long-term anti-inflammatory and anti-thrombotic capability. The inner layer consists of PCL-PEG-PCL [triblock copolymer of polyethylene glycol and poly(ε-caprolactone)]/Au-heparin electrospun fibers encapsulated with indomethacin while the outer layer is composed of polyvinyl alcohol (PVA) and ROS-responsive poly(2-(4-((2,6-dimethoxy-4-methylphenoxy)methyl)phenyl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane) (PBA) fibers. In response to acute inflammation after vascular injury, the outer layer reduces ROS rapidly by PBA degradation for inflammation suppression. The degraded outer layer facilitates inner layer reconstruction with enhanced hemocompatibility through the H-bond between PVA and PCL-PEG-PCL. Furthermore, chronic inflammation is effectively depressed with the sustained release of indomethacin from the inner layer. The substantial enhancement of the functional integrity of implants and reduction of thrombotic and inflammatory complications with the self-adaptive ECM are demonstrated both in vitro and in vivo. Our work paves a new way to develop long-term anti-thrombotic and anti-inflammatory implants with self-adaption and self-regulation properties.

CD34+CD146+ adipose-derived stromal cells enhance engraftment of transplanted fat

Fat grafting is a surgical technique able to reconstruct and regenerate soft tissue. The adipose‐derived stromal cells (ASCs) within the stromal vascular fraction are believed to drive these beneficial effects. ASCs are increasingly recognized to be a heterogeneous group, comprised of multiple stem and progenitor subpopulations with distinct functions. We hypothesized the existence of an ASC subpopulation with enhanced angiogenic potential. Human ASCs that were CD34+CD146+, CD34+CD146−, or CD34+ unfractionated (UF) were isolated by flow cytometry for comparison of expression of proangiogenic factors and endothelial tube‐forming potential. Next, lipoaspirate was enriched with either CD34+CD146+, CD34+CD146−, CD34+ UF ASCs, or was not enriched, and grafted beneath the scalp skin of immunodeficient CD‐1 Nude mice (10 000 cells/200 μL/graft). Fat retention was monitored radiographically more than 8 weeks and fat grafts were harvested for histological assessment of quality and vascularization. The CD34+CD146+ subpopulation comprised ~30% of ASCs, and exhibited increased expression of vascular endothelial growth factor and angiopoietin‐1 compared to CD34+CD146− and CD34+ UF ASCs, and increased expression of fibroblast growth factor‐2 compared to CD34+CD146− ASCs. The CD34+CD146+ subpopulation exhibited enhanced induction of tube‐formation compared to CD34+CD146− ASCs. Upon transplantation, fat enriched CD34+CD146+ ASCs underwent less resorption and had improved histologic quality and vascularization. We have identified a subpopulation of CD34+ ASCs with enhanced angiogenic effects in vitro and in vivo, likely mediated by increased expression of potent proangiogenic factors. These findings suggest that enriching lipoaspirate with CD34+CD146+ ASCs may enhance fat graft vascularization and retention in the clinical setting.

Osteochondral Regeneration Using Adipose Tissue-Derived Mesenchymal Stem Cells

Osteoarthritis (OA) is a major joint disease that promotes locomotor deficiency during the middle- to old-age, with the associated disability potentially decreasing quality of life. Recently, surgical strategies to reconstruct both articular cartilage and subchondral bone for OA have been diligently investigated for restoring joint structure and function. Adipose tissue-derived mesenchymal stem cells (AT-MSCs), which maintain pluripotency and self-proliferation ability, have recently received attention as a useful tool to regenerate osteocartilage for OA. In this review, several studies were described related to AT-MSC spheroids, with scaffold and scaffold-free three-dimensional (3D) constructs produced using “mold” or “Kenzan” methods for osteochondral regeneration. First, several examples of articular cartilage regeneration using AT-MSCs were introduced. Second, studies of osteochondral regeneration (not only cartilage but also subchondral bone) using AT-MSCs were described. Third, examples were presented wherein spheroids were produced using AT-MSCs for cartilage regeneration. Fourth, osteochondral regeneration following autologous implantation of AT-MSC scaffold-free 3D constructs, fabricated using the “mold” or “Kenzan” method, was considered. Finally, prospects of osteochondral regeneration by scaffold-free 3D constructs using AT-MSC spheroids were discussed.

Pure polylysine-based foamy scaffolds and their interaction with MC3T3-E1 cells and osteogenesis

Polypeptide-derived copolymers have widely been exploited for drug/gene delivery due to their pendant functional groups and non-toxic degradation products. However, fabrication of polypeptide-based scaffolds for tissue engineering has seldom been reported. In this study, foamy poly(N _ε -benzyl formateoxycarbonyl-L-Lysine) (PZL) and poly(N _ε -benzyl formateoxycarbonyl-L-lysine-co-L-phenylalanine) (PZLP) scaffolds were successfully prepared by a combination of ring-opening polymerization of α-amino acid N-carboxyanhydride and negative porous NaCl templating approach. The physicochemical properties of these scaffolds including glass transition temperature, contact angle, compression modulus and degradation behavior were characterized. Both in vitro and in vivo biocompatibility of the scaffolds were evaluated by MC3T3-E1 cell culture and SD subcutaneous model, respectively. The results from live-dead staining, MTT and ALP activity assays indicated that PZL scaffolds were more conducive to the adhesion, proliferation and osteoblastic differentiation of MC3T3-E1 cells compared to PZLP scaffolds in the initial culture period due to their specific surface properties. While porous structure rather than surface properties of scaffolds played a decisive role in the later stage of cell culture. The results of in vivo studies including H&E, Masson's trichrome and CD34 staining further demonstrated that PZL scaffolds supported the ingrowth of microvessels than PZLP scaffolds due to their surface property difference. Collectively, PZL scaffolds displayed good biocompatibility and could be a promising candidate for tissue engineering application.

Plasma Surface Polymerized and Biomarker Conjugated Boron Nitride Nanoparticles for Cancer-Specific Therapy: Experimental and Theoretical Study

A new low-pressure plasma-based approach to activate the surface of BN nanoparticles (BNNPs) in order to facilitate the attachment of folate acid (FA) molecules for cancer-specific therapy is described. Plasma treatment of BNNPs (BNNPs^PT) was performed in a radiofrequency plasma reactor using ethylene and carbon dioxide monomers. The carboxyl groups deposited on the surface of BNNPs^PT were activated by N,N'-dicyclohexylcarbodiimide (DCC) and participated in the condensation reaction with ethylene diamine (EDA) to form a thin amino-containing layer (EDA-BNNP^PT). Then, the DCC-activated FA was covalently bonded with BNNPs^PT by a chemical reaction between amino groups of EDA-BNNPs^PT and carboxyl groups of FA. Density functional theory calculations showed that the pre-activation of FA by DCC is required for grafting of the FA to the EDA-BNNPs^PT. It was also demonstrated that after FA immobilization, the electronic characteristics of the pteridine ring remain unchanged, indicating that the targeting properties of the FA/EDA-BNNPs^PT nanohybrids are preserved.

Optimizing the decellularization process of an upper limb skeletal muscle; implications for muscle tissue engineering

Upper limb muscle reconstruction is required following cancer resection, trauma, and congenital deformities. Current surgical reconstruction of the muscle involves local, regional and free flaps. However, muscle reconstruction is not always possible due to the size of the defect and functional donor site morbidity. These challenges could be addressed with the production of scaffolds composed of an extracellular matrix (ECM) derived from decellularized human skeletal muscle. This study aimed to find an optimal technique to decellularize a flexor digitorum superficialis muscle. The first two protocols were based on a detergent only (DOT) and a detergent-enzymatic protocol (DET). The third protocol avoided the use of detergents and proteolytic enzymes (NDNET). The decellularized scaffolds were characterized using qualitative techniques including histological and immunofluorescent staining and quantitative techniques assessing deoxyribonucleic acid (DNA), glycosaminoglycan (GAG), and collagen content. The DOT protocol consisting of 2% SDS for 4 hours was successful at decellularizing human FDS, as shown by DNA content assay and nuclei immunofluorescence staining. The DOT protocol maintained the microstructure of the scaffolds as shown by Masson's trichrome staining and collagen and GAG content. DET and NDNET protocols maintained the ECM, but were unsuccessful in removing all DNA content after two cycles of decellularization. Decellularization of skeletal muscle is a viable option for muscle reconstruction using a detergent only technique for upper limb defects. Further testing in vivo will assess the effectiveness of decellularized scaffolds for upper limb muscle skeletal tissue engineering.

Argon plasma modification promotes adipose derived stem cells osteogenic and chondrogenic differentiation on nanocomposite polyurethane scaffolds; implications for skeletal tissue engineering

Bone and cartilage craniofacial defects due to trauma or congenital deformities pose a difficult problem for reconstructive surgeons. Human adipose stem cells (ADSCs) can differentiate into bone and cartilage and together with suitable scaffolds could provide a promising system for skeletal tissue engineering. It has been suggested that nanomaterials can direct cell behavior depending on their surface nanotopographies. Thus, this study examined whether by altering a nanoscaffold surface using radiofrequency to excite gases, argon (Ar), nitrogen (N₂) and oxygen (O₂) with a single step technique, we could enhance the osteogenic and chondrogenic potential of ADSCs. At 24 h, Ar modification promoted the highest increase in ADSCs adhesion as indicated by upregulation of vinculin and focal adhesion kinase (FAK) expression compared to O₂ and N₂ scaffolds. Furthermore, ADSCs on Ar-modified nanocomposite polymer POSS-PCU scaffolds upregulated expression of bone markers, alkaline phosphatase, collagen I and osteocalcin after 3 weeks. Cartilage markers, aggrecan and collagen II, were also upregulated on Ar-modified scaffolds at the mRNA and protein level. Finally, all plasma treated scaffolds supported tissue ingrowth and angiogenesis after grafting onto the chick chorioallantoic membrane. Ar promoted greater expression of vascular endothelial growth factor and laminin in ovo compared to O₂ and N₂ scaffolds as shown by immunohistochemistry. This study provides an important understanding into which surface chemistries best support the osteogenic and chondrogenic differentiation of ADSCs that could be harnessed for regenerative skeletal applications. Argon surface modification is a simple tool that can promote ADSC skeletal differentiation that is easily amenable to translation into clinical practice.

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Bone and cartilage craniofacial defects due to trauma or congenital deformities pose a challenging problem for reconstructive surgeons.

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Nanomaterials can direct adipose derived stem cell (ADSC) differentiation depending on their surface nanotopographies.

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This study demonstrates that Argon surface modification improve the chondrogenesis and osteogenesis of ADSCs.

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Argon surface modification is a tool that can upregulate ADSC skeletal differentiation and is amenable to translation into clinical practice.

Optimizing the decellularization process of human maxillofacial muscles for facial reconstruction using a detergent-only approach

Trauma, congenital diseases, and cancer resection cause muscle deformities of the human facial muscle. Muscle defects are either treated with local or distal flaps if direct closure is not possible. However, such surgical interventions are limited by donor morbidity and limited tissue availability. Decellularized scaffolds provide alternative strategies for replacing and restoring missing facial muscle by creating scaffolds that mimic the native tissue. This study aimed to develop a protocol to decellularize human zygomaticus major muscle (ZMM) and masseter muscle (MM). Three protocols were assessed including a detergent-only treatment (DOT), detergent-enzymatic treatment (DET) protocol, and a third nondetergent nonenzymatic treatment protocol. Scaffolds were then characterized via histological, immunofluorescent, and quantitative techniques to assess which protocol provided optimal decellularization and maintenance of the extracellular matrix (ECM). The results demonstrated three cycles of DOT protocol consisting of 2% sodium dodecyl sulfate for 4 hr was optimal for decellularization for both ZMM and MM. After three cycles, DNA content was significantly reduced compared with native ZMM and MM (p < .05) with preservation of collagen and glycosaminoglycan content and ECM on histological analysis. DET and nondetergent nonenzymatic treatment protocols were unsuccessful in decellularizing the ZMM and MM with residual DNA content after four cycles and caused ECM disruption on histological analysis. All protocols did not impair the mechanical properties and supported human fibroblast growth. In conclusion, the DOT protocol is effective in producing human decellularized muscle scaffolds that maintain the ECM. Further investigation of detergent only decellurization techniques should be explored as a first step to create effective scaffolds for muscle tissue engineering.

Argon plasma modified nanocomposite polyurethane scaffolds provide an alternative strategy for cartilage tissue engineering

Background

Children born with a small or absent ear undergo surgical reconstruction to create a suitable replacement using rib cartilage. To overcome the donor site morbidity and long-term pain of harvesting rib cartilage, synthetic materials can be a useful alternative. Medpor, is the currently used synthetic polyethylene material to replace missing facial cartilage but unfortunately it has high levels of surgical complications including infection and extrusion, making it an unsuitable replacement. New materials for facial cartilage reconstruction are required to improve the outcomes of surgical reconstruction. This study has developed a new nanomaterial with argon surface modification for auricular cartilage replacement to overcome the complications with Medpor.

Results

Polyurethanes nanocomposites scaffolds (PU) were modified with argon plasma surface modification (Ar) and compared to Medpor in vitro and in vivo. Ar scaffolds allowed for greater protein adsorption than Medpor and PU after 48 h (p < 0.05). Cell viability and DNA assays demonstrated over 14-days greater human dermal fibroblast adhesion and cell growth on Ar than PU and Medpor nanocomposites scaffolds (p < 0.05). Gene expression using RT-qPCR of collagen-I, fibronectin, elastin, and laminin was upregulated on Ar scaffolds compared to Medpor and PU after 14-days (p < 0.05). Medpor, unmodified polyurethane and plasma modified polyurethane scaffolds were subcutaneously implanted in the dorsum of mice for 12 weeks to assess tissue integration and angiogenesis. Subcutaneous implantation of Ar scaffolds in mice dorsum, demonstrated significantly greater tissue integration by H&E and Massons trichrome staining, as well as angiogenesis by CD31 vessel immunohistochemistry staining over 12-weeks (p < 0.05).

Conclusions

Argon modified polyurethane nanocomposite scaffolds support cell attachment and growth, tissue integration and angiogenesis and are a promising alternative for facial cartilage replacement. This study demonstrates polyurethane nanocomposite scaffolds with argon surface modification are a promising biomaterial for cartilage tissue engineering applications.

Electronic supplementary material

The online version of this article (10.1186/s12951-019-0477-z) contains supplementary material, which is available to authorized users.

Argon plasma surface modification promotes the therapeutic angiogenesis and tissue formation of tissue-engineered scaffolds in vivo by adipose-derived stem cells

Background

Synthetic implants are being used to restore injured or damaged tissues following cancer resection and congenital diseases. However, the survival of large tissue implant replacements depends on their ability to support angiogenesis that if limited, causes extrusion and infection of the implant. This study assessed the beneficial effect of platelet-rich plasma (PRP) and adipose-derived stem cells (ADSCs) on synthetic biomaterials in combination with argon plasma surface modification to enhance vascularisation of tissue-engineered constructs.

Methods

Non-biodegradable polyurethane scaffolds were manufactured and modified with plasma surface modification using argon gas (PM). Donor rats were then used to extract ADSCs and PRP to modify the scaffolds further. Scaffolds with and without PM were modified with and without ADSCs and PRP and subcutaneously implanted in the dorsum of rats for 3 months. After 12 weeks, the scaffolds were excised and the degree of tissue integration using H&E staining and Masson’s trichrome staining, angiogenesis by CD31 and immune response by CD45 and CD68 immunohistochemistry staining was examined.

Results

H&E and Masson’s trichrome staining showed PM+PRP+ADSC and PM+ADSC scaffolds had the greatest tissue integration, but there was no significant difference between the two scaffolds (p < 0.05). The greatest vessel formation after 3 months was shown with PM+PRP+ADSC and PM+ADSC scaffolds using CD31 staining compared to all other scaffolds (p < 0.05). The CD45 and CD68 staining was similar between all scaffolds after 3 months showing the ADSCs or PRP had no effect on the immune response of the scaffolds.

Conclusions

Argon plasma surface modification enhanced the effect of adipose-derived stem cells effect on angiogenesis and tissue integration of polyurethane scaffolds. The combination of ADSCs and argon plasma modification may improve the survival of large tissue implants for regenerative applications.

Electronic supplementary material

The online version of this article (10.1186/s13287-019-1195-z) contains supplementary material, which is available to authorized users.

Biotechnological Management of Angiopathic Wounds: Challenges and Perspectives

Angiopathic wound is a wound that develops as a result of a local vascular lesion. Angiogenesis is an important aspect underlying repair, and increased angiogenesis could accelerate and improve the healing outcome. Biotherapy has been used more and more in clinic and brings hope for angiopathic wound treatment, through the rapid recovery of angiogenesis and regulation and correction of the whole wound microenvironment. In this article, we discuss the advantages and disadvantages of various technologies ranging from presentation of angiogenic growth factors, genetic strategies, stem cells, and biomaterials engineering in angiopathic wound treatment.

Argon plasma improves the tissue integration and angiogenesis of subcutaneous implants by modifying surface chemistry and topography

BACKGROUND

Tissue integration and vessel formation are important criteria for the successful implantation of synthetic biomaterials for subcutaneous implantation.

OBJECTIVE

We report the optimization of plasma surface modification (PSM) using argon (Ar), oxygen (O2) and nitrogen (N2) gases of a polyurethane polymer to enhance tissue integration and angiogenesis.

METHODS

The scaffold's bulk and surface characteristics were compared before and after PSM with either Ar, O2 and N2. The viability and adhesion of human dermal fibroblasts (HDFs) on the modified scaffolds were compared. The formation of extracellular matrix by the HDFs on the modified scaffolds was evaluated. Scaffolds were subcutaneously implanted in a mouse model for 3 months to analyze tissue integration, angiogenesis and capsule formation.

RESULTS

Surface analysis demonstrated that interfacial modification (chemistry, topography and wettability) achieved by PSM is unique and varies according to the gas used. O2 plasma led to extensive changes in interfacial properties, whereas Ar treatment caused moderate changes. N2 plasma caused the least effect on surface chemistry of the polymer. PSM-treated scaffolds significantly (P<0.05) enhanced HDF activity and growth over 21 days. Among all three gases, Ar modification showed the highest protein adsorption. Ar-modified scaffolds also showed a significant upregulation of adhesion-related proteins (vinculin, focal adhesion kinase, talin and paxillin; P<0.05) and extracellular matrix marker genes (collagen type I, fibronectin, laminin and elastin) and deposition of associated proteins by the HDFs. Subcutaneous implantation after 3 months demonstrated the highest tissue integration and angiogenesis and the lowest capsule formation on Ar-modified scaffolds compared with O2- and N2-modified scaffolds.

CONCLUSION

PSM using Ar is a cost-effective and efficient method to improve the tissue integration and angiogenesis of subcutaneous implants.

Evaluation of Sterilisation Techniques for Regenerative Medicine Scaffolds Fabricated with Polyurethane Nonbiodegradable and Bioabsorbable Nanocomposite Materials

An effective sterilisation technique that maintains structure integrity, mechanical properties, and biocompatibility is essential for the translation of new biomaterials to the clinical setting. We aimed to establish an effective sterilisation technique for a biodegradable (POSS-PCL) and nonbiodegradable (POSS-PCU) nanocomposite scaffold that maintains stem cell biocompatibility. Scaffolds were sterilised using 70% ethanol, ultraviolet radiation, bleach, antibiotic/antimycotic, ethylene oxide, gamma irradiation, argon plasma, or autoclaving. Samples were immersed in tryptone soya broth and thioglycollate medium and inspected for signs of microbial growth. Scaffold surface and mechanical and molecular weight properties were investigated. AlamarBlue viability assay of adipose derived stem cells (ADSC) seeded on scaffolds was performed to investigate metabolic activity. Confocal imaging of rhodamine phalloidin and DAPI stained ADSCs was performed to evaluate morphology. Ethylene oxide, gamma irradiation, argon plasma, autoclaving, 70% ethanol, and bleach were effective in sterilising the scaffolds. Autoclaving, gamma irradiation, and ethylene oxide led to a significant change in the molecular weight distribution of POSS-PCL and gamma irradiation and ethylene oxide to that of POSS-PCU (p<0.05). UV, ethanol, gamma irradiation, and ethylene oxide caused significant changes in the mechanical properties of POSS-PCL (p<0.05). Argon was associated with significantly higher surface wettability and ADSC metabolic activity (p<0.05). In this study, argon plasma was an effective sterilisation technique for both nonbiodegradable and biodegradable nanocomposite scaffolds. Argon plasma should be further investigated as a potential sterilisation technique for medical devices.

Silsesquioxane polymer as a potential scaffold for laryngeal reconstruction

Cancer, disease and trauma to the larynx and their treatment can lead to permanent loss of structures critical to voice, breathing and swallowing. Engineered partial or total laryngeal replacements would need to match the ambitious specifications of replicating functionality, outer biocompatibility, and permissiveness for an inner mucosal lining. Here we present porous polyhedral oligomeric silsesquioxane-poly(carbonate urea) urethane (POSS-PCUU) as a potential scaffold for engineering laryngeal tissue. Specifically, we employ a precipitation and porogen leaching technique for manufacturing the polymer. The polymer is chemically consistent across all sample types and produces a foam-like scaffold with two distinct topographies and an internal structure composed of nano- and micro-pores. While the highly porous internal structure of the scaffold contributes to the complex tensile behaviour of the polymer, the surface of the scaffold remains largely non-porous. The low number of pores minimise access for cells, although primary fibroblasts and epithelial cells do attach and proliferate on the polymer surface. Our data show that with a change in manufacturing protocol to produce porous polymer surfaces, POSS-PCUU may be a potential candidate for overcoming some of the limitations associated with laryngeal reconstruction and regeneration.

POSS-enhanced thermosensitive hybrid hydrogels for cell adhesion and detachment

Thermosensitive poly(N-isopropylacrylamide) (PNIPAM)-based substrates have presented great promise in cell sheet engineering. However, non-functionalized PNIPAM cannot be well applied for cell cultivation, due to the low cell adhesion. Herein, to enhance PNIPAM-based substrates and to promote cell proliferation and detachment, a polyhedral oligomeric silsesquioxane (POSS) nanoscale inorganic enhanced agent has been introduced into PNIPAM matrices to construct POSS-containing hybrid hydrogels. The hydrogels were facilely prepared using POSS as a cross-linker via one-pot crosslinking reaction under UV irradiation. The swelling behavior, thermal stability and the mechanical properties of POSS–PNIPAM hybrid hydrogels have been evaluated and they are all dependent on the content of POSS. The in vitro experiment confirms that human amniotic mesenchymal stem cells (hAMSCs) exhibit clearly enhanced adhesion and proliferation on the substrates of POSS–PNIPAM hybrid hydrogels in comparison to the pure PNIPAM hydrogel without POSS. Based on the thermal-responsiveness of PNIPAM, the proliferated cells are easily released without damage from the surface of hybrid hydrogels. Therefore, POSS-enhanced PNIPAM hybrid hydrogels provide a unique approach for harvesting anchorage dependent stem cells.

Thermosensitive poly(N-isopropylacrylamide) (PNIPAM)-based substrates have presented great promise in cell sheet engineering.

Protein Interactions with Nanoengineered Polyoxazoline Surfaces Generated via Plasma Deposition

Protein adsorption to biomaterials is critical in determining their suitability for specific applications, such as implants or biosensors. Here, we show that surface nanoroughness can be tailored to control the covalent binding of proteins to plasma-deposited polyoxazoline (PPOx). Nanoengineered surfaces were created by immobilizing gold nanoparticles varying in size and surface density on PPOx films. To keep the surface chemistry consistent while preserving the nanotopography, all substrates were overcoated with a nanothin PPOx film. Bovine serum albumin was chosen to study protein interactions with the nanoengineered surfaces. The results demonstrate that the amount of protein bound to the surface is not directly correlated with the increase in surface area. Instead, it is determined by nanotopography-induced geometric effects and surface wettability. A densely packed array of 16 and 38 nm nanoparticles hinders protein adsorption compared to smooth PPOx substrates, while it increases for 68 nm nanoparticles. These adaptable surfaces could be used for designing biomaterials where proteins adsorption is or is not desirable.

Chemical group-dependent plasma polymerisation preferentially directs adipose stem cell differentiation towards osteogenic or chondrogenic lineages

Human adipose derived stem cells (ADSCs) are being explored for the repair of craniofacial defects due to their multi-differentiation potential and ease of isolation and expansion. Crucial to using ADSCs for craniofacial repair is the availability of materials with appropriate biomechanical properties that can support their differentiation into bone and cartilage. We tested the hypothesis that different modifications of chemical groups on the surface of a nanocomposite polymer could increase human ADSC adhesion and selectively enhance their osteogenic and chondrogenic differentiation. We show that the COOH modification significantly promoted initial cell adhesion and proliferation over 14 days compared to NH₂ surfaces. Expression of focal adhesion kinase and vinculin was enhanced after plasma surface polymerisation at 24 h. The COOH modification significantly enhanced chondrogenic differentiation as indicated by up-regulation of aggrecan and collagen II transcripts. In contrast, NH₂ group functionalised scaffolds promoted osteogenic differentiation with significantly enhanced expression of collagen I, alkaline phosphatase and osteocalcin both at the gene and protein level. Finally, chorioallantoic membrane grafting demonstrated that both NH₂ and COOH functionalised scaffolds seeded with ADSCs were biocompatible and supported vessel ingrowth apparently to a greater degree than unmodified scaffolds. In summary, our study shows the ability to direct ADSC chondrogenic and osteogenic differentiation by deposition of different chemical groups through plasma surface polymerisation. Hence this approach could be used to selectively enhance bone or cartilage formation before implantation in vivo to repair skeletal defects.

Statement of Significance

Human adipose derived stem cells (hADSCs) are an exciting stem cell source for regenerative medicine due to their plentiful supply and ease of isolation. However, the optimal environmental cues to direct stem cells towards certain lineages change have to has not been identified. We have shown that by modifying the surface of the scaffold with specific chemical groups using plasma surface polymerisation techniques we can control ADSCs differentiation. This study shows that ADSCs can be differentiated towards osteogenic and chondrogenic lineages on amine (NH₂) and carboxyl (COOH) modified scaffolds respectively. Plasma polymerisation can be easily applied to other biomaterial surfaces to direct stem cell differentiation for the regeneration of bone and cartilage.

Manipulating tumor hypoxia toward enhanced photodynamic therapy (PDT)

This mini-review summarizes various methods for overcoming or utilizing hypoxia for enhanced PDT.

The effects of nanotopography and coculture systems to promote angiogenesis for wound repair

Insufficient angiogenesis in severe wounds delays wound repair because of a lack of blood supply to the wound site. Therefore, pro-angiogenic therapeutics may enhance wound repair. Many studies have investigated various physical and biochemical cues to improve angiogenesis, such as biocompatible materials, surface modifications, angiogenic factors and coculture systems using various cell types. However, the present capability to mimic the micro- and nanostructure of the natural microenvironment, particularly its porous, fibrous features, is limited. Nanotopography may represent a promising tool to overcome these limitations. Here, we discuss various approaches to the use of nanotopography to enhance angiogenesis and consider the combination of coculture systems with nanotopography to mimic the native environment for promotion of angiogenesis in wound healing and repair.

Plasma Surface Modification of Polyhedral Oligomeric Silsequioxane-Poly(carbonate-urea) Urethane with Allylamine Enhances the Response and Osteogenic Differentiation of Adipose-Derived Stem Cells

This study present amino functionalization of biocompatible polymer polyhedral oligomeric silsequioxane-poly(carbonate-urea) urethane (POSS-PCU) using plasma polymerization process to induce osteogenic differentiation of adipose derived stem cells (ADSCs). Optimization of plasma polymerization process was carried out keeping cell culture application in mind. Thus, samples were rigorously tested for retention of amino groups under both dry and wet conditions. Physio-chemical characterization was carried out using ninhydrin test, X-ray photon spectroscopy, scanning electron microscopy, and static water contact analysis. Results from physio chemical characterization shows that functionalization of the amino group is not stable under wet conditions and optimization of plasma process is required for stable bonding of amino groups to the POSS-PCU polymer. Optimized samples were later tested in vitro in short and long-term culture to study differentiation of ADSCs on amino modified samples. Short-term cell culture shows that initial cell attachment was significantly (p < 0.001) improved on amine modified samples (NH2-POSS-PCU) compared to unmodified POSS-PCU. NH2-POSS-PCU samples also facilitates osteogenic differentiation of ADSCs as confirmed by immunological staining of cells for extracellular markers such as collagen Type I and osteopontin. Quantification of total collagen and ALP activity also shows significant (p < 0.001) increase on NH2-POSS-PCU samples compared to unmodified POSS-PCU. A pilot study also confirms that these optimized amino modified POSS-PCU samples can further be functionalized using bone inducing peptide such as KRSR using conventional wet chemistry. This further provides an opportunity for biofunctionalization of the polymer for various tissue specific applications.

Current and emerging vascularization strategies in skin tissue engineering

Vascularization is a key process in skin tissue engineering, determining the biological function of artificial skin implants. Hence, efficient vascularization strategies are a major prerequisite for the safe application of these implants in clinical practice. Current approaches include (i) modification of structural and physicochemical properties of dermal scaffolds, (ii) biological scaffold activation with growth factor-releasing systems or gene vectors, and (iii) generation of prevascularized skin substitutes by seeding scaffolds with vessel-forming cells. These conventional approaches may be further supplemented by emerging strategies, such as transplantation of adipose tissue-derived microvascular fragments, 3D bioprinting and microfluidics, miRNA modulation, cell sheet engineering, and fabrication of photosynthetic scaffolds. The successful translation of these vascularization strategies from bench to bedside may pave the way for a broad clinical implementation of skin tissue engineering.