Corneal disease is the main cause of blindness and keratoplasty is the only widely accepted treatment. Shortage of donor tissue makes the biomaterials for corneal regeneration a hot area of research. Collagen is the main component of corneal stroma, so collagen becomes a promising material for corneal repair. However, due to the drawbacks of collagen, it needs to be further modified to satisfy the requirement of corneal regeneration. In this article, we highlight the importance of collagen materials for corneal repair, and summarize several methods of preparing collagen based corneal regeneration materials, including chemical crosslinking, plastic compression of collagen, and collagen vitrigel. These modification methods can make collagen membranes with remarkable properties such as enough mechanical and suture retention strength, antibacterial property and excellent optical property. These materials may provide potential treatment for corneal disease.
Biocompatibility is the basic requirement of biomaterials for tissue repair. However, the present concept of biocompatibility has a certain limitation in explaining the phenomena involved in biomaterial-based tissue repair. New materials, in particular those for tissue engineering and regeneration, have been developed with common characteristics, i.e. they participate deeply into important chemical and biological processes in the human body and the interaction between the biomaterials and tissues is far more complex. Understanding the interplay between these biomaterials and tissues is vital for their development and functionalization. Herein, we suggest the concept of bioadaptability of biomaterials. This concept describes the three most important aspects that can determine the performance of biomaterials in tissue repair： 1） the adaptability of the micro-environment created by biomaterials to the native microenvironment in situ; 2） the adaptability of the mechanical properties of biomaterials to the native tissue; 3） the adaptability of the degradation properties of biomaterials to the new tissue formation. The concept of bioadaptability emphasizes both the material＇s characteristics and biological aspects within a certain micro-environment and molecular mechanism. It may provide new inspiration to uncover the interaction mechanism of biomaterials and tissues, to foster the new ideas of functionalization of biomaterials and to investigate the fundamental issues during the tissue repair process by biomaterials. Furthermore, designing biomaterials with such bioadaptability would open a new door for repairing and regenerating organs or tissues. In this review, we summarized the works in recent years on the bioadaptability of biomaterials for tissue repair applications.
Gelatin/Alginate hydrogels were engineered for bioplotting in tissue engineering. One major drawback of hydrogel scaffolds is the lack of adequate mechanical properties. In this study, using a bioplotter, we constructed the scaffolds with different pore architectures by deposition of gelatin/alginate hydrogels layerby-layer. The scaffolds with different crosslinking degree were obtained by post-crosslinking methods. Their physicochemical properties, as well as cell viability, were assessed. Different crosslinking methods had little influence on scaffold architecture, porosity, pore size and distribution. By contrast, the water absorption ability, degradation rate and mechanical properties of the scaffolds were dramatically affected by treatment with various concentrations of crosslinking agent （glutaraldehyde）. The crosslinking process using glutaraldehyde markedly improved the stability and mechanical strength of the hydrogel scaf- folds. Besides the post-processing methods, the pore architecture can also evidently affect the mechanical properties of the scaffolds. The crosslinked gelatin/alginate scaffolds showed a good potential to encap-sulate cells or drugs.
Titanium （Ti） nanorods fabricated using selective corrosion of Ti substrate by anodic technology show better biocompatibility with pre-osteoblast cells. The current study investigated the response of the murine pre-osteoblast cell MCST3-E1 on Ti nanorod topography and untreated Ti surfaces by means of examination of the morphology and osteogenic differentiation responsible for the pre-osteoblast reaction. The morphology of MCST3-E1 cells was observed using scanning electron microscopy, and alkaline phosphatase （ALP） activity was measured using a colorimetric assay after incubation for 7, 14, and 21 days. The expression of three osteogenic differentiation markers including ALP, osteocalcin （OCN）, and collagen type 1A1 （COL1A1） and two transcription factors including runt related transcription factor 2 （Runx2） and osterix （Osx） at different time points was detected using real-time polymerase chain reaction analysis in both groups. Osx was used to confirm the protein level. The results showed that Ti nanorod surfaces provided prolonged higher levels of ALP activity compared with unmodified Ti surface on the 14th and 21st days. Gene expression analysis of ALP, OCN, and COL1A1 showed significant upregulation with modified nanorod topography after incubation for 14 and 21 days. Osteogenic transcription factors of Runx2 and Osx exhibited changes consistent with the osteogenic differentiation markers, and this may contribute to the persistently active differentiation of MC3T3-E1 cells in the Ti nanorod group. These results demonstrated that the current nanostructured surface may be considered bioadaptive topography to control cellular behaviors and osteoblast differentiation. The in vivo performance and applicability are further required to investigate osseointegration between implant and host bone in the early stages for prevention of aseptic implant loosening.
In this research, polypyrrole nanocone arrays doped with β-Naphthalene sulphonic acid （PPy-NSA） were built. This film was expected to control protein adsorption and bacterial adhesion by potential-induced reversibly redox. The scanning Kelvin probe microscopy （SKPM） and surface contact angles （SCA） tests suggested that the surface potential and wettability of PPy-NSA nanocone arrays could be controlled by simply controlling its redox property via applying potential. The controllable surface potential and wettability in return controlled the adsorption of protein and adhesion of bacteria. The proposed material might find application in the preparation of smart biomaterial surfaces that can regulate proteins and bacterial adhesion by a simple potential switching.
Zhengnan ZhouWeiping LiTianrui HePeng YuGuoxin TanChengyun Ning
The objective of this study was to determine the role of functional groups of silane coupling on bioactive titanium （Ti） surface by electrochemical deposition, and calcium phosphate （CAP） coating, as well as bone cell adhesion and proliferation. Methyl group （-CH3）, amino group （-NH2）, and epoxy group （-glyph name--C（O）C） were introduced onto the bioactive Ti surface using self-assembled monolayers （SAMs） with different silane coupling agents as molecular bridges. The effect of the surface functional groups on the growth features of the CaP crystals was analyzed （including chemical compositions, element content, minerals morphology and crystal structure etc.）. CH3-terminated SAMs showed a hydrophobic surface and others were hydrophilic by contact angle measurement; NH2-terminated SAMs showed a positive charge and others were negatively charged using zeta-potential measurement. Scanning electron microscopy results confirmed that flower-like structure coatings consisting of various pinpoint-like crystals were formatted by different functional groups of silane coupling, and the CaP coatings were multicrystalline consisting of hydroxyapatite （HA） and precursors. CaP coating of CH3-terminated SAMs exhibited more excellent crystallization property as compared to coatings of --NH2 and -C（O）C groups. In vitro MC3T3- El cells adhesion and proliferation were performed. The results showed that CaP coatings on silane coupling functionalized surfaces supported cell adhesion and proliferation. Thus, these functional groups of silane coupling on Ti can form homogeneous and oriented nano-CaP coatings and provide a more biocompatible surface for bone regeneration and biomedical applications.
Guoxin TanKongyou OuyangHang WangLei ZhouXiaolan WangYan LiuLan ZhangChengyun Ning
