Osteogenesis of human adipose-derived stem cells on poly(dopamine)-coated electrospun poly(lactic acid) fiber mats

Mussel-inspired polydopamine modified mica with enhanced mechanical strength and thermal performance of poly(lactic acid) coating

Polylactic acid (PLA), as a green functional polymer, has been useful in various coating applications. However, due to the low mechanical strength and thermal stability of PLA, it needs to be improved in order to expand its application areas. In this work, a series of polylactic acid (PLA) nanocomposite films were prepared through introducing polydopamine-modified mica (PDA@MICA) as a self-assemble nanofiller to enhance its mechanical and thermal properties. The results demonstrated that PLA/PDA@MICA shows excellent mechanical properties. Tensile tests showed that PLA/PDA@MICA exhibits a 58.3 % increase in tensile strength and a 16.8 % increase in Young's modulus compared to pure PLA. Meanwhile, thermal performance testing shown the introduction of PDA@MICA led to an increase in crystallinities (Xc = 24.78 %). And the thermal decomposition temperature of PLA/PDA@MICA film (374 °C) was slightly higher than that of PLA film (367 °C). The simultaneous improvement of the mechanical and thermal properties was attributed to the formation of hydrogen bonds between PLA and PDA@MICA. In addition, the parallel arrangement of PDA@MICA and PLA macromolecular chains forms a unique "brick and mortar" structure in the coating, which enhances the mechanical properties of PLA/PDA@MICA composite coatings. This study reports a successful approach to simultaneously address the drawbacks of PLA, specifically its low thermal stability and mechanical strength, thereby promoting its widespread application in the coatings industry.

Bioinspired core-shell nanofiber drug-delivery system modulates osteogenic and osteoclast activity for bone tissue regeneration

Osteogenic-osteoclast coupling processes play a crucial role in bone regeneration. Recently, strategies that focus on multi-functionalized implant surfaces to enhance the healing of bone defects through the synergistic regulation of osteogenesis and osteoclastogenesis is still a challenging task in the field of bone tissue engineering. The aim of this study was to create a dual-drug release-based core-shell nanofibers with the intent of achieving a time-controlled release to facilitate bone regeneration. We fabricated core-shell P/PCL nanofibers using coaxial electrospinning, where alendronate (ALN) was incorporated into the core layer and hydroxyapatite (HA) into shell. The surface of the nanofiber construct was further modified with mussel-derived polydopamine (PDA) to induce hydrophilicity and enhance cell interactions. Surface characterizations confirmed the successful synthesis of PDA@PHA/PCL-ALN nanofibers endowed with excellent mechanical strength (20.02 ± 0.13 MPa) and hydrophilicity (22.56°), as well as the sustained sequential release of ALN and Ca ions. In vitro experiments demonstrated that PDA-functionalized core-shell PHA/PCL-ALN scaffolds possessed excellent cytocompatibility, enhanced cell adhesion and proliferation, alkaline phosphatase activity and osteogenesis-related genes. In addition to osteogenesis, the engineered scaffolds also significantly reduced osteoclastogenesis, such as tartrate-resistant acid phosphatase activity and osteoclastogenesis-related gene expression. After 12-week of implantation, it was observed that PDA@PHA/PCL-ALN nanofiber scaffolds, in a rat cranial defect model, significantly promoted bone repair and regeneration. Microcomputed tomography, histological examination, and immunohistochemical analysis collectively demonstrated that the PDA-functionalized core-shell PHA/PCL-ALN scaffolds exhibited exceptional osteogenesis-inducing and osteoclastogenesis-inhibiting effects. Finally, it may be concluded from our results that the bio-inspired surface-functionalized multifunctional, biomimetic and controlled release core-shell nanofiber provides a promising strategy to facilitate bone healing.

Aligned Electroactive Electrospun Fibrous Scaffolds for Peripheral Nerve Regeneration

Effective repair and functional recovery of large peripheral nerve deficits are urgent clinical needs. A biofunctional electroactive scaffold typically acts as a "bridge" for the repair of large nerve defects. In this study, we constructed a biomimetic piezoelectric and conductive aligned polypyrrole (PPy)/polydopamine (PDA)/poly-l-lactic acid (PLLA) electrospun fibrous scaffold to improve the hydrophilicity and cellular compatibility of PLLA and restore the weakened piezoelectric effect of PDA, which is beneficial in promoting Schwann cell differentiation and dorsal root ganglion neuronal extension and alignment. The aligned PPy/PDA/PLLA fibrous scaffold bridged the sciatic nerve of Sprague-Dawley rats with a 10 mm deficit, prevented autotomy, and promoted nerve regeneration and functional recovery, thereby activating the calcium and AMP-activated protein kinase signaling pathways. Therefore, electroactive fibrous scaffolds exhibit great potential for neural tissue regeneration.

Mussel-inspired polydopamine decorated silane modified-electroconductive gelatin-PEDOT:PSS scaffolds for bone regeneration

This study seeks to simulate both the chemistry and piezoelectricity of bone by synthesizing electroconductive silane-modified gelatin-poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) scaffolds using the freeze drying technique. In order to enhance hydrophilicity, cell interaction, and biomineralization, the scaffolds were functionalized with polydopamine (PDA) inspired by mussels. Physicochemical, electrical, and mechanical analyses were conducted on the scaffolds, as well as in vitro evaluations using the osteosarcoma cell line MG-63. It was found that scaffolds had interconnected porous structures, so the PDA layer formation reduced the size of pores while maintaining scaffold uniformity. PDA functionalization reduced the electrical resistance of the constructs while improving their hydrophilicity, compressive strength, and modulus. As a result of the PDA functionalization and the use of silane coupling agents, higher stability and durability were achieved as well as an improvement in biomineralization capability after being soaked in SBF solution for a month. Additionally, the PDA coating enabled the constructs to enhance viability, adhesion, and proliferation of MG-63 cells, as well as to express alkaline phosphatase and deposit HA, indicating that scaffolds can be used for bone regeneration. Therefore, the PDA-coated scaffolds developed in this study and the non-toxic performance of PEDOT:PSS present a promising approach for further in vitro and in vivo studies.

How Mechanical and Physicochemical Material Characteristics Influence Adipose-Derived Stem Cell Fate

Adipose-derived stem cells (ASCs) are a subpopulation of mesenchymal stem cells. Compared to bone marrow-derived stem cells, they can be harvested with minimal invasiveness. ASCs can be easily expanded and were shown to be able to differentiate into several clinically relevant cell types. Therefore, this cell type represents a promising component in various tissue engineering and medical approaches (e.g., cell therapy). In vivo cells are surrounded by the extracellular matrix (ECM) that provides a wide range of tissue-specific physical and chemical cues, such as stiffness, topography, and chemical composition. Cells can sense the characteristics of their ECM and respond to them in a specific cellular behavior (e.g., proliferation or differentiation). Thus, in vitro biomaterial properties represent an important tool to control ASCs behavior. In this review, we give an overview of the current research in the mechanosensing of ASCs and current studies investigating the impact of material stiffens, topography, and chemical modification on ASC behavior. Additionally, we outline the use of natural ECM as a biomaterial and its interaction with ASCs regarding cellular behavior.

Dual-functional composite scaffolds for inhibiting infection and promoting bone regeneration

The treatment of infected bone defects is an intractable problem in orthopedics. It comprises two critical parts, namely that of infection control and bone defect repair. According to these two core tasks during treatment, the ideal approach of simultaneously controlling infection and repairing bone defects is promising treatment strategy. Several engineered biomaterials and drug delivery systems with dual functions of anti-bacterial action and ostogenesis-promotion have been developed and demonstrated excellent therapeutic effects. Compared with the conventional treatment method, the dual-functional composite scaffold can provide one-stage treatment avoiding multiple surgeries, thereby remarkably simplifying the treatment process and reducing the treatment time, overcoming the disadvantages of conventional bone transplantation. In this review, the impaired bone repair ability and its specific mechanisms in the microenvironment of pathogen infection and excessive inflammation were analyzed, providing a theoretical basis for the treatment of infectious bone defects. Furthermore, we discussed the composite dual-functional scaffold composed of a combination of antibacterial and osteogenic material. Finally, a series of advanced drug delivery systems with antibacterial and bone-promoting capabilities were summarized and discussed. This review provides a comprehensive understanding for the microenvironment of infectious bone defects and leading-edge design strategies for the antibacterial and bone-promoting dual-function scaffold, thus providing clinically significant treatment methods for infectious bone defects.

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Antibacterial and bone-promoting dual-function scaffolds are ideal strategies for treatment of infectious bone defects.

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The effect of infection on bone repair was summarized in detail from four important aspects.

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A variety of dual-function scaffolds based on antibacterial and osteogenic materials were discussed.

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Dual-function drug delivery systems promoting repair of infectious bone defects by locally releasing functional agents.

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Leading-edge design strategies, challenges and prospects for dual-functional biomaterials were provided.

Mussel-inspired polydopamine decorated alginate dialdehyde-gelatin 3D printed scaffolds for bone tissue engineering application

This study utilized extrusion-based 3D printing technology to fabricate calcium-cross-linked alginate dialdehyde-gelatin scaffolds for bone regeneration. The surface of polymeric constructs was modified with mussel-derived polydopamine (PDA) in order to induce biomineralization, increase hydrophilicity, and enhance cell interactions. Microscopic observations revealed that the PDA layer homogeneously coated the surface and did not appear to induce any distinct change in the microstructure of the scaffolds. The PDA-functionalized scaffolds were more mechanically stable (compression strength of 0.69 ± 0.02 MPa) and hydrophilic (contact angle of 26) than non-modified scaffolds. PDA-decorated ADA-GEL scaffolds demonstrated greater durability. As result of the 18-days immersion in simulated body fluid solution, the PDA-coated scaffolds showed satisfactory biomineralization. Based on theoretical energy analysis, it was shown that the scaffolds coated with PDA interact spontaneously with osteocalcin and osteomodulin (binding energy values of −35.95 kJ mol⁻¹ and −46.39 kJ mol⁻¹, respectively), resulting in the formation of a protein layer on the surface, suggesting applications in bone repair. PDA-coated ADA-GEL scaffolds are capable of supporting osteosarcoma MG-63 cell adhesion, viability (140.18% after 7 days), and proliferation. In addition to increased alkaline phosphatase secretion, osteoimage intensity also increased, indicating that the scaffolds could potentially induce bone regeneration. As a consequence, the present results confirm that 3D printed PDA-coated scaffolds constitute an intriguing novel approach for bone tissue engineering.

Functionalization of Electrospun Nanofiber for Bone Tissue Engineering

Bone-tissue engineering is an alternative treatment for bone defects with great potential in which scaffold is a critical factor to determine the effect of bone regeneration. Electrospun nanofibers are widely used as scaffolds in the biomedical field for their similarity with the structure of the extracellular matrix (ECM). Their unique characteristics are: larger surface areas, porosity and processability; these make them ideal candidates for bone-tissue engineering. This review briefly introduces bone-tissue engineering and summarizes the materials and methods for electrospining. More importantly, how to functionalize electrospun nanofibers to make them more conducive for bone regeneration is highlighted. Finally, the existing deficiencies of functionalized electrospun nanofibers for promoting osteogenesis are proposed. Such a summary can lay the foundation for the clinical practice of functionalized electrospun nanofibers.

Metal Ion Augmented Mussel Inspired Polydopamine Immobilized 3D Printed Osteoconductive Scaffolds for Accelerated Bone Tissue Regeneration

Critical bone defects with a sluggish rate of auto-osteoconduction and imperfect reconstruction are motivators for the development of an alternate innovative approach for the regeneration of bone. Tissue engineering for bone regeneration signifies an advanced way to overcome this problem by creating an additional bone tissue substitute. Among different fabrication techniques, the 3D printing technique is obviously the most efficient and advanced way to fabricate an osteoconductive scaffold with a controlled porous structure. In the current article, the polycarbonate and polyester diol based polyurethane-urea (P12) was synthesized and 3D porous nanohybrid scaffolds (P12/TP-nHA) were fabricated using the 3D printing technique by incorporating the osteoconductive nanomaterial titanium phosphate adorned nanohydroxyapatite (TP-nHA). To improve the bioactivity, the surface of the fabricated scaffolds was modified with the immobilized biomolecule polydopamine (PDA) at room temperature. XPS study as well as the measurement of surface wettability confirmed the higher amount of PDA immobilization on TP-nHA incorporated nanohybrid scaffolds through the dative bone formation between the vacant d orbital of the incorporated titanium ion and the lone pair electron of the catechol group of dopamine. The incorporated titanium phosphate (TP) increased the tensile strength (53.1%) and elongation at break (96.8%) of the nanohybrid composite as compared to pristine P12. Moreover, the TP incorporated nanohybrid scaffold with calcium and phosphate moieties and a higher amount of immobilized active biomolecule improved the in vitro bioactivity, including the cell viability, cell proliferation, and osteogenic gene expression using hMSCs, of the fabricated nanohybrid scaffolds. A rat tibia defect model depicted that the TP incorporated nanohybrid scaffold with immobilized PDA enhanced the in vivo bone regeneration ability compared to the control sample without revealing any organ toxicity signifying the superior osteogenic bioactivity. Thus, a TP augmented polydopamine immobilized polyurethane-urea based nanohybrid 3D printed scaffold with improved physicochemical properties and osteogenic bioactivity could be utilized as an excellent advanced material for bone regeneration substitute.

An osteogenic bioink composed of alginate, cellulose nanofibrils, and polydopamine nanoparticles for 3D bioprinting and bone tissue engineering

Bioprinting is an emerging technology for manufacturing cell-laden three-dimensional (3D) scaffolds, which are used to fabricate complex 3D constructs and provide specific microenvironments for supporting cell growth and differentiation. The development of bioinks with appropriate printability and specific bioactivities is crucial for bioprinting and tissue engineering applications, including bone tissue regeneration. Therefore, to produce functional bioinks for osteoblast printing and bone tissue formation, we formulated various nanocomposite hydrogel-based bioinks using natural and biocompatible biomaterials (i.e., alginate, tempo-oxidized cellulose nanofibrils (TOCNF), and polydopamine nanoparticles (PDANPs)). Rheological studies and printability tests revealed that bioinks containing 1.5% alginate and 1.5% TOCNF in the presence or absence of PDANP (0.5%) are suitable for 3D printing. Furthermore, in vitro studies of 3D-printed osteoblast-laden scaffolds indicated that the 0.5% PDANP-incorporated bioink induced significant osteogenesis. Overall, the bioink consisting of alginate, TOCNF, and PDANPs exhibited excellent printability and bioactivity (i.e., osteogenesis).

Polycatecholamine and gentamicin as modifiers for antibacterial and blood-biocompatible polyester vascular prostheses

Polyester (PET) prostheses are commonly used in reconstructive vascular surgery. The most serious complication after implantation is early or late infection of the graft. Therefore, there is high demand to protect prosthesis against bacterial adhesion and biofilm development. For this reason, in this work PET prostheses were first coated by highly adhesive polycatecholamine layer. The grafts were then coupled with gentamicin and studied in relation to morphological and structural properties, biological safety (contact with blood, reaction of vascular endothelial cells (HUVEC), Danio rerio fish), drug release and antibacterial activity. Among two tested catecholamine monomers, L-DOPA was found to be more effective precursor in this process than dopamine. For L-DOPA, assistance of Cu²⁺, Mg²⁺ and Na⁺ ions seems to increase the amount of further immobilized drug. Coated prostheses exhibited greater human endothelial cell proliferation increase and lower cytotoxic effect than uncoated. The modification reduced the hemolysis observed for pristine commercial graft and limited the rate of abnormalities in D. rerio larvae, confirming the safety of the proposed modification. The coating allowed to double the amount of immobilized antibiotic in comparison with uncoated graft which resulted in increased antibacterial activity and reduced bacterial adhesion against 4 bacterial strains prevalent in biomaterials infections. Overall, poly(L-DOPA)-coatings deposited on PET vascular grafts can effectively functionalize these prostheses for higher safety in biomedical applications.

Polydopamine-Coated Poly(l-lactide) Nanofibers with Controlled Release of VEGF and BMP-2 as a Regenerative Periosteum

The periosteum plays an important role in vascularization and ossification during bone repair. However, in most studies, an artificial periosteum cannot restore both functions of the periosteum concurrently. In this study, a novel nanofiber that can sustain the release of vascular endothelial growth factor (VEGF) and bone morphogenetic protein-2 (BMP-2) was fabricated to enhance the durability of angiogenesis and osteogenesis during bone regeneration. A cell-free tissue engineered periosteum based on an electrospinning poly-l-lactic acid (PLLA) nanofiber was fabricated, on which VEGF and BMP-2 were immobilized through a polydopamine (PDA) coating conveniently and safely (BVP@PLLA membrane). The results indicated a significantly improved loading rate as well as a slow and sustained release of VEGF and BMP-2 with the help of the PDA coating. BMP-2 immobilized on nanofibers successfully induced the osteogenic differentiation of human bone marrow mesenchymal stem cells (BMSCs) in vitro with high expression of runt-related transcription factor 2 (Runx2), osteopontin (OPN), and alkaline phosphatase (ALP). Similarly, angiogenic differentiation of BMSCs with the expression of fetal liver kinase-1 (Flk-1) and vascular endothelial cadherin (VE-cadherin) was observed under the environment of VEGF sustained release. Moreover, an in vivo study revealed that the BVP@PLLA membrane could enhance vascular formation and new bone formation, which accelerates bone regeneration in rat femoral defects along with a massive periosteum defect. Therefore, our study suggests that the novel artificial periosteum with dual growth factor controlled release is a promising system to improve bone regeneration in bone defects along with a massive periosteum defect.

Applications of Polydopamine-Modified Scaffolds in the Peripheral Nerve Tissue Engineering

Peripheral nerve injury is a common and complicated traumatic disease in clinical neurosurgery. With the rapid advancement and development of medical technologies, novel tissue engineering provides alternative therapies such as nerve conduit transplantation. It has achieved significant outcomes. The scaffold surface modification is vital to the reconstruction of a pro-healing interface. Polydopamine has high chemical activity, adhesion, hydrophilicity, hygroscopicity, stability, biocompatibility, and other properties. It is often used in the surface modification of biomaterials, especially in the peripheral nerve regeneration. The present review discusses that polydopamine can promote the adhesion, proliferation, and differentiation of neural stem cells and the growth of neuronal processes. Polydopamine is widely used in the surface modification of nerve conduits and has a potential application prospect of repairing peripheral nerve injury. Polydopamine-modified scaffolds are promising in the peripheral nerve tissue engineering.

Melanin and Melanin-Like Hybrid Materials in Regenerative Medicine

Melanins are a group of dark insoluble pigments found widespread in nature. In mammals, the brown-black eumelanins and the reddish-yellow pheomelanins are the main determinants of skin, hair, and eye pigmentation and play a significant role in photoprotection as well as in many biological functions ensuring homeostasis. Due to their broad-spectrum light absorption, radical scavenging, electric conductivity, and paramagnetic behavior, eumelanins are widely studied in the biomedical field. The continuing advancements in the development of biomimetic design strategies offer novel opportunities toward specifically engineered multifunctional biomaterials for regenerative medicine. Melanin and melanin-like coatings have been shown to increase cell attachment and proliferation on different substrates and to promote and ameliorate skin, bone, and nerve defect healing in several in vivo models. Herein, the state of the art and future perspectives of melanins as promising bioinspired platforms for natural regeneration processes are highlighted and discussed.

Mussel-inspired polydopamine-mediated surface modification of freeze-cast poly (ε-caprolactone) scaffolds for bone tissue engineering applications

There are many methods used to fabricate the scaffolds for tissue regeneration, among which freeze casting has attracted a great deal of attention due to the capability to create a unidirectional structure. In this study, polycaprolactone (PCL) scaffolds were fabricated by freeze-casting technology in order to create porous microstructure with oriented open-pore channels. To induce biomineralization, and to improve hydrophilicity and cell interactions, mussel-inspired polydopamine (PDA) was coated on the surface of the freeze-cast PCL constructs. Then, the synergistic effects of oriented microstructure and deposited layer on efficient reconstruction of injured bone were studied. Microscopic observations demonstrated that, the coated layer did not show any special change in lamellar microstructure of the scaffolds. Water-scaffold interactions were evaluated by contact angle measurements, and they demonstrated strong enhancement in the hydrophilicity of the polymeric scaffolds after PDA coating. Biodegradation ratio and water uptake evaluation confirmed an increase in the measured values after PDA precipitation. The biomineralization of the PDA-coated scaffolds was characterized by field-emission scanning electron microscopy (FE-SEM), energy dispersive X-ray (EDX) and X-ray diffraction (XRD). Obtained results confirmed biomineralization of the constructs after a 28-day immersion in a simulated body fluid (SBF) solution. Mechanical analysis demonstrated higher compressive strength after PDA coating. L929 fibroblast cell viability and attachment illustrated that PDA-coated PCL scaffolds are able to support cell adhesion and proliferation. The increased secretion of alkaline phosphatase (ALP) after culturing osteosarcoma cell lines (MG-63) revealed the initial capability of scaffolds to induce bone regeneration. Therefore, the PDA-coated scaffolds introduce a promising approach for bone tissue engineering application.

Application of Nanomaterials in Regulating the Fate of Adipose-derived Stem Cells

Adipose-derived stem cells are adult stem cells which are easy to obtain and multi-potent. Stem-cell therapy has become a promising new treatment for many diseases, and plays an increasingly important role in the field of tissue repair, regeneration and reconstruction. The physicochemical properties of the extracellular microenvironment contribute to the regulation of the fate of stem cells. Nanomaterials have stable particle size, large specific surface area and good biocompatibility, which has led them being recognized as having broad application prospects in the field of biomedicine. In this paper, we review recent developments of nanomaterials in adipose-derived stem cell research. Taken together, the current literature indicates that nanomaterials can regulate the proliferation and differentiation of adipose-derived stem cells. However, the properties and regulatory effects of nanomaterials can vary widely depending on their composition. This review aims to provide a comprehensive guide for future stem-cell research on the use of nanomaterials.

Oxidized chitosan modified electrospun scaffolds for controllable release of acyclovir

Developing a novel scaffold carrier with a sustained and controllable release profile of drug is essential to promote the effective transdermal delivery for acyclovir (ACY). In this work, electrospun polyacrylonitrile nanofibers (PAN NFs) was chemically modified with oxidized chitosan (OC). The modified fibrous scaffold was further loaded with the ACY for drug released investigation. FT-IR and NMR results revealed that the conversion of the functional group for each step has successfully occurred on the surface of the fibers. Through the in-vitro drug release and kinetic study, it demonstrated that ACY could be sustainably and controlled released from the OC modified scaffold following the Korsmeyer-Peppas model with a Fickian diffusion mechanism. The human adipose-derived stem cells and the blood combability evaluation confirmed the obtained scaffold possessed excellent cell biocompatibility and hemocompatibility. It could be concluded that the resultant OC modified scaffold based on electrospun PAN NFs opened a new potential option for the topical/transdermal drug delivery of ACY.

The effect of oxygen plasma pretreatment on the properties of mussel-inspired polydopamine-decorated polyurethane nanofibers

In this study, polyurethane (PU) scaffolds were fabricated by electrospinning technology and modified through the deposition of polydopamine (PDA) on the activated surface under oxygen plasma treatment. Herein, the effect of the modification process on the homogeneous surface coating and the changes in the physicochemical and biological properties were evaluated. Morphological observations demonstrated decoration of the nanofibrous microstructure with PDA, while the uniformity and homogeneity of the deposited layer increased after plasma oxygen treatment. Hydrophilicity measurements and swelling ratio indicated a remarkable improvement in the interaction of scaffolds with water molecules when the PDA coating is applied on the surface of the treated nanofibers. The biomineralization of the samples was characterized using X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM) images. It was found that PDA has the capability for mineralization, and the amount of deposited hydroxyapatite increased as a function of PDA content. The in vitro evaluation of constructs indicated great improvement in cell-scaffold interactions, biocompatibility, and alkaline phosphatase activity after coating the PDA on the plasma-modified matrix. These results suggest that PDA coating, especially after oxygen plasma treatment, improves the physicochemical and in vitro properties of PU scaffolds for bone tissue engineering application.

Engineering 3D degradable, pliable scaffolds toward adipose tissue regeneration; optimized printability, simulations and surface modification

We present a solution to regenerate adipose tissue using degradable, soft, pliable 3D-printed scaffolds made of a medical-grade copolymer coated with polydopamine. The problem today is that while printing, the medical grade copolyesters degrade and the scaffolds become very stiff and brittle, being not optimal for adipose tissue defects. Herein, we have used high molar mass poly(L-lactide-co-trimethylene carbonate) (PLATMC) to engineer scaffolds using a direct extrusion-based 3D printer, the 3D Bioplotter®. Our approach was first focused on how the printing influences the polymer and scaffold's mechanical properties, then on exploring different printing designs and, in the end, on assessing surface functionalization. Finite element analysis revealed that scaffold's mechanical properties vary according to the gradual degradation of the polymer as a consequence of the molar mass decrease during printing. Considering this, we defined optimal printing parameters to minimize material's degradation and printed scaffolds with different designs. We subsequently functionalized one scaffold design with polydopamine coating and conducted in vitro cell studies. Results showed that polydopamine augmented stem cell proliferation and adipogenic differentiation owing to increased surface hydrophilicity. Thus, the present research show that the medical grade PLATMC based scaffolds are a potential candidate towards the development of implantable, resorbable, medical devices for adipose tissue regeneration.

Current progress in application of polymeric nanofibers to tissue engineering

Tissue engineering uses a combination of cell biology, chemistry, and biomaterials to fabricate three dimensional (3D) tissues that mimic the architecture of extracellular matrix (ECM) comprising diverse interwoven nanofibrous structure. Among several methods for producing nanofibrous scaffolds, electrospinning has gained intense interest because it can make nanofibers with a porous structure and high specific surface area. The processing and solution parameters of electrospinning can considerably affect the assembly and structural morphology of the fabricated nanofibers. Electrospun nanofibers can be made from natural or synthetic polymers and blending them is a straightforward way to tune the functionality of the nanofibers. Furthermore, the electrospun nanofibers can be functionalized with various surface modification strategies. In this review, we highlight the latest achievements in fabricating electrospun nanofibers and describe various ways to modify the surface and structure of scaffolds to promote their functionality. We also summarize the application of advanced polymeric nanofibrous scaffolds in the regeneration of human bone, cartilage, vascular tissues, and tendons/ligaments.

Additive Manufacturing of Nerve Decellularized Extracellular Matrix-Contained Polyurethane Conduits for Peripheral Nerve Regeneration

The nervous system is the part of our body that plays critical roles in the coordination of actions and sensory information as well as communication between different body parts through electrical signal transmissions. Current studies have shown that patients are likely to experience a functional loss if they have to go through a nerve repair for >15 mm lesion. The ideal treatment methodology is autologous nerve transplant, but numerous problems lie in this treatment method, such as lack of harvesting sites. Therefore, researchers are attempting to fabricate alternatives for nerve regeneration, and nerve conduit is one of the potential alternatives for nerve regeneration. In this study, we fabricated polyurethane/polydopamine/extracellular matrix (PU/PDA/ECM) nerve conduits using digital light processing (DLP) technology and assessed for its physical properties, biodegradability, cytocompatibility, neural related growth factor, and proteins secretion and expression and its potential in allowing cellular adhesion and proliferation. It was reported that PU/PDA/ECM nerve conduits were more hydrophilic and allowed enhanced cellular adhesion, proliferation, expression, and secretion of neural-related proteins (collagen I and laminin) and also enhanced expression of neurogenic proteins, such as nestin and microtubule-associated protein 2 (MAP2). In addition, PU/PDA/ECM nerve conduits were reported to be non-cytotoxic, had sustained biodegradability, and had similar physical characteristics as PU conduits. Therefore, we believed that PU/PDA/ECM nerve conduits could be a potential candidate for future nerve-related research or clinical applications.

In vitro behavior of tendon stem/progenitor cells on bioactive electrospun nanofiber membranes for tendon-bone tissue engineering applications

Purpose

In order to accelerate the tendon-bone healing processes and achieve the efficient osteointegration between the tendon graft and bone tunnel, we aim to design bioactive electrospun nanofiber membranes combined with tendon stem/progenitor cells (TSPCs) to promote osteogenic regeneration of the tendon and bone interface.

Methods

In this study, nanofiber membranes of polycaprolactone (PCL), PCL/collagen I (COL-1) hybrid nanofiber membranes, poly(dopamine) (PDA)-coated PCL nanofiber membranes and PDA-coated PCL/COL-1 hybrid nanofiber membranes were successfully fabricated by electrospinning. The biochemical characteristics and nanofibrous morphology of the membranes, as well as the characterization of rat TSPCs, were defined in vitro. After co-culture with different types of electrospun nanofiber membranes in vitro, cell proliferation, viability, adhesion and osteogenic differentiation of TSPCs were evaluated at different time points.

Results

Among all the membranes, the performance of the PCL/COL-1 (volume ratio: 2:1 v/v) group was superior in terms of its ability to support the adhesion, proliferation, and osteogenic differentiation of TSPCs. No benefit was found in this study to include PDA coating on cell adhesion, proliferation and osteogenic differentiation of TSPCs.

Conclusion

The PCL/COL-1 hybrid electrospun nanofiber membranes are biocompatible, biomimetic, easily fabricated, and are capable of supporting cell adhesion, proliferation, and osteogenic differentiation of TSPCs. These bioactive electrospun nanofiber membranes may act as a suitable functional biomimetic scaffold in tendon-bone tissue engineering applications to enhance tendon-bone healing abilities.

Biomineralization guided by polydopamine-modifed poly(L-lactide) fibrous membrane for promoted osteoconductive activity

A method to mediate biomineralization of electrospinning poly(L-lactide) (PLLA) fibrous membrane assisted by polydopamine (PDA) coating was developed to obtain enhanced osteoconductive activity. The biomineralization mechanism, surface composition, morphology and hydrophilicity of the original and modified PLLA fibrous membranes were characterized. Results revealed that the PDA coating effectively accelerated the formation of hydroxyapatite (HA) on PLLA fibrous membrane and resulted a great increase in hydrophilicity. Moreover, the tensile property of PLLA fibrous membrane was enhanced by the PDA coating while almost kept unchanged by further immobilized with HA. Cells culture results indicated that the successive introduction of PDA and HA contributed to an obvious improvement in the adhesion and proliferation, as well as up-regulated alkaline phosphatase (ALP) activity and promoted osteogenic-related genes and proteins expression of MC3T3-E1 cells. Overall, the as-prepared PLLA-PDA-HA fibrous membrane can be expected as a favorable scaffold for bone tissue repair.

The mussel-inspired assisted apatite mineralized on PolyJet material for artificial bone scaffold

With the development of three-dimensional (3D) printing, many commercial 3D printing materials have been applied in the fields of biomedicine and medical. MED610 is a clear, biocompatible PolyJet material that is medically certified for bodily contact. In this study, the polydopamine (PDA)/hydroxyapatite (HA) coating was added to the printed MED610 objects to evaluate its physical properties, cell proliferation, cell morphology, and alkaline phosphatase expression level. The results show that the PDA/HA coating helps printed objects to enhance the hardness, biocompatibility, and osteogenic differentiation potential. We expect that PDA/HA coatings contribute to the applicability of MED610 in biomedical and medical applications.

Indocyanine green based fluorescent polymeric nanoprobes for in vitro imaging

Indocyanine green (ICG) provides an advantage in the imaging of deep tumors as it can reach deeper location without being absorbed in the upper layers of biological tissues in the wavelengths, which named "therapeutic window" in the tissue engineering. Unfortunately, rapid elimination and short-term stability in aqueous media limited its use as a fluorescence probe for the early detection of cancerous tissue. In this study, stabilization of ICG was performed by encapsulating ICG molecules into the biodegradable polymer composited with poly(l-lactic acid) and poly(ε-caprolactone) via a simple one-step multiaxial electrospinning method. Different types of coaxial and triaxial structure groups were performed and compared with single polymer only groups. Confocal microscopy was used to image the encapsulated ICG (1 mg/mL) within electrospun nanofibers and in vitro ICG uptake by MIA PaCa-2 pancreatic cancer cells. Stability of encapsulated ICG is demonstrated by the in vitro sustainable release profile in PBS (pH = 4 and 7) up to 21 days. These results suggest the potential of the ability of internalization and accommodation of ICG into the pancreatic cell cytoplasm from in vitro implanted ICG-encapsulated multiaxial nanofiber mats. ICG-encapsulated multilayer nanofibers may be promising for the local sustained delivery system to eliminate loss of dosage caused by direct injection of ICG-loaded nanoparticles in systemic administration.

Physicochemical and biological investigation of oxygen plasma modified electrospun polyurethane scaffolds for connective tissue engineering application

In this study, electrospinning was selected to fabricate randomly oriented polyurethane (PU) nanofibers for tissue engineering application, and the surface of scaffolds was exposed to oxygen plasma flow. The morphology structure of the PU scaffolds before and after oxygen plasma treatment was observed using scanning electron microscopy (SEM) micrographs, and the fiber diameter distribution was measured using Image J software. The results demonstrated that oxygen plasma modification reduces the fiber diameter without any other special effects on fiber microstructure. Water drop contact angle and swelling ratio of PU constructs were performed to estimate the water-scaffolds interactions. The results revealed improvement of hydrophilicity by oxygen plasma treatment. Atomic force microscopy test was done to analyze a topological characteristic of the scaffolds, and it was found out that oxygen plasma treatment decreases the roughness of the scaffolds. The biological behavior of the scaffolds was investigated by SEM observation and MTT assay after L-929 fibroblast cells culture. In vitro assays demonstrated biocompatibility, cellular attachments, and filopodia formation on plasma modified samples. These results suggest that oxygen plasma treatment improves the physicochemical and biological properties of PU scaffolds to create a more hydrophilic surface which facilitates cell attachments and proliferation.

Mussel-Inspired Nanostructures Potentiate the Immunomodulatory Properties and Angiogenesis of Mesenchymal Stem Cells

The therapeutic effects of mesenchymal stem cells (MSCs)-material constructs mainly come from the secretion of trophic factors from MSCs, especially the immunomodulatory and angiogenic cytokines. Recent findings indicate the significance of topographical cues from these materials in modulating paracrine functions of MSCs. Here, we developed functionalized three-dimensional-printed bioceramic (BC) scaffolds with a mussel-inspired surface coating in order to regulate the paracrine function of adipose-derived MSCs (Ad-MSCs). We found that Ad-MSCs cultured on polydopamine-modified BC scaffolds (DOPA-BC) significantly produced more immunomodulatory and pro-angiogenic factors when compared with those cultured on BC scaffolds or microplates. Functional assays, such as endothelial progenitor cells migration, tube formation, and macrophage polarization, were performed to confirm the enhanced paracrine functions of the secreted trophic factors from Ad-MSCs cultured on DOPA-BC scaffolds. Further investigation identified that both focal adhesion kinase- and extracellular signal-related kinase signaling were the required mechano-transduction pathways through which the mussel-inspired surface stimulated the paracrine effect of Ad-MSCs. In a diabetic skin-defect-healing model in rats, conditioned medium received from the Ad-MSCs cultured on DOPA-BC sped wound closure, enhanced vascularization, and promoted macrophage switching from a proinflammatory M1 to a pro-healing and anti-inflammatory M2 phenotype in the wound bed. These results demonstrate that a bio-inspired coating with polydopamine represents an effective method to enhance the paracrine function of MSCs. Our findings illustrate a novel strategy to accelerate tissue regeneration by guiding the paracrine-signaling network.

3D-Printed Bioactive Calcium Silicate/Poly-ε-Caprolactone Bioscaffolds Modified with Biomimetic Extracellular Matrices for Bone Regeneration

Currently, clinically available orthopedic implants are extremely biocompatible but they lack specific biological characteristics that allow for further interaction with surrounding tissues. The extracellular matrix (ECM)-coated scaffolds have received considerable interest for bone regeneration due to their ability in upregulating regenerative cellular behaviors. This study delves into the designing and fabrication of three-dimensional (3D)-printed scaffolds that were made out of calcium silicate (CS), polycaprolactone (PCL), and decellularized ECM (dECM) from MG63 cells, generating a promising bone tissue engineering strategy that revolves around the concept of enhancing osteogenesis by creating an osteoinductive microenvironment with osteogenesis-promoting dECM. We cultured MG63 on scaffolds to obtain a dECM-coated CS/PCL scaffold and further studied the biological performance of the dECM hybrid scaffolds. The results indicated that the dECM-coated CS/PCL scaffolds exhibited excellent biocompatibility and effectively enhanced cellular adhesion, proliferation, and differentiation of human Wharton's Jelly mesenchymal stem cells by increasing the expression of osteogenic-related genes. They also presented anti-inflammatory characteristics by showing a decrease in the expression of tumor necrosis factor-alpha (TNF-α) and interleukin-1 (IL-1). Histological analysis of in vivo experiments presented excellent bone regenerative capabilities of the dECM-coated scaffold. Overall, our work presented a promising technique for producing bioscaffolds that can augment bone tissue regeneration in numerous aspects.

Polydopamine modification of silk fibroin membranes significantly promotes their wound healing effect

Natural polymer-based wound dressings have gained great attention in skin tissue engineering.

The Physicochemical Properties of Decellularized Extracellular Matrix-Coated 3D Printed Poly(ε-caprolactone) Nerve Conduits for Promoting Schwann Cells Proliferation and Differentiation

Although autologous nerve grafting remains the gold standard treatment for peripheral nerve injuries, alternative methods such as development of nerve guidance conduits have since emerged and evolved to counter the many disadvantages of nerve grafting. However, the efficacy and viability of current nerve conduits remain unclear in clinical trials. Here, we focused on a novel decellularized extracellular matrix (dECM) and polydopamine (PDA)-coated 3D-printed poly(ε-caprolactone) (PCL)-based conduits, whereby the PDA surface modification acts as an attachment platform for further dECM attachment. We demonstrated that dECM/PDA-coated PCL conduits possessed higher mechanical properties when compared to human or animal nerves. Such modifications were proved to affect cell behaviors. Cellular behaviors and neuronal differentiation of Schwann cells were assessed to determine for the efficacies of the conduits. There were some cell-specific neuronal markers, such as Nestin, neuron-specific class III beta-tubulin (TUJ-1), and microtubule-associated protein 2 (MAP2) analyzed by enzyme-linked immunosorbent assay, and Nestin expressions were found to be 0.65-fold up-regulated, while TUJ1 expressions were 2.3-fold up-regulated and MAP2 expressions were 2.5-fold up-regulated when compared to Ctl. The methodology of PDA coating employed in this study can be used as a simple model to immobilize dECM onto PCL conduits, and the results showed that dECM/PDA-coated PCL conduits can as a practical and clinically viable tool for promoting regenerative outcomes in larger peripheral nerve defects.

Surface Modification of Calcium Silicate via Mussel-Inspired Polydopamine and Effective Adsorption of Extracellular Matrix to Promote Osteogenesis Differentiation for Bone Tissue Engineering

Calcium silicate-based cement has garnered huge interest in recent years, due to its versatility and potential in mass fabrication of a variety of bioceramics. For this study, the main objective was to fabricate functionalized calcium silicate (CS) powder integrated with a simple bio-inspired surface modification using polydopamine (PDA), to regulate cellular behaviors such as cellular adhesion, and subsequently cell differentiation and proliferation. For this study, scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) techniques were used to analyze the chemical compositions and observe the surface characteristics of our PDA coated CS cements. Such modifications were found to enhance Wharton Jelly's mesenchymal stem cells (WJMSC) in various ways. Firstly, PDA-coated CS cements were found to significantly enhance cell adhesion with higher expressions of cell adhesion markers, such as focal adhesion kinase and integrins. This was further supported by morphology analysis of the cells. This enhanced cell adhesion, in turn, led to significantly higher secretion of extracellular matrix (ECM) proteins, such as collagen I and fibronectin, which directly promoted cell attachments and proliferation. In our osteogenesis assays, it was found that secretion and expression of osteogenesis related genes and proteins were significantly higher and were dependent on the PDA content. Therefore, these results demonstrated that such simple bio-inspired modification techniques of synthetic degradable CS cements can be applied as a future modification, to modify and convert inert surfaces of synthetic bone grafts to enhance and modulate the cell behaviors of WJMSCs. This in turn can be used as a potential alternative for further bioengineering research.

Influence of the nanofiber chemistry and orientation of biodegradable poly(butylene succinate)-based scaffolds on osteoblast differentiation for bone tissue regeneration

Innovative nanofibrous scaffolds have attracted considerable attention in bone tissue engineering, due to their ability to mimic the hierarchical architecture of an extracellular matrix. Aiming at investigating how the polymer chemistry and fiber orientation of electrospun scaffolds (ES) based on poly(butylene succinate) (PBS) and poly(butylene succinate/diglycolate) (P(BS80BDG20)) affect human osteoblast differentiation, uniaxially aligned (a-) and randomly (r-) distributed nanofibers were produced. Although human osteoblastic SAOS-2 cells were shown to be viable and adherent onto all ES materials, a-P(BS80BDG20) exhibited the best performance both in terms of cellular phosphorylated focal adhesion kinase expression and in terms of alkaline phosphatase activity, calcified bone matrix deposition and quantitative gene expression of bone specific markers during differentiation. It has been hypothesized that the presence of ether linkages may lead to an increased density of hydrogen bond acceptors along the P(BS80BDG20) backbone, which, by interacting with cell membrane components, can in turn promote a better cell attachment on the copolymer mats with respect to the PBS homopolymer. Furthermore, although displaying the same chemical structure, r-P(BS80BDG20) scaffolds showed a reduced cell attachment and osteogenic differentiation in comparison with a-P(BS80BDG20), evidencing the importance of nanofiber alignment. Thus, the coupled action of polymer chemical structure and nanofiber alignment played a significant role in promoting the biological interaction.

Electrospun Silk Fibroin Nanofibrous Scaffolds with Two-Stage Hydroxyapatite Functionalization for Enhancing the Osteogenic Differentiation of Human Adipose-Derived Mesenchymal Stem Cells

The development of functional scaffolds with improved osteogenic potential is important for successful bone formation and mineralization in bone tissue engineering. In this study, we developed a functional electrospun silk fibroin (SF) nanofibrous scaffold functionalized with two-stage hydroxyapatite (HAp) particles, using mussel adhesive-inspired polydopamine (PDA) chemistry. HAp particles were first incorporated into SF scaffolds during the electrospinning process, and then immobilized onto the electrospun SF nanofibrous scaffolds containing HAp via PDA-mediated adhesive chemistry. We obtained two-stage HAp-functionalized SF nanofibrous scaffolds with improved mechanical properties and capable of providing a bone-specific physiological microenvironment. The developed scaffolds were tested for their ability to enhance the osteogenic differentiation of human adipose-derived mesenchymal stem cells (hADMSCs) in vitro and repair bone defect in vivo. To boost their ability for bone repair, we genetically modified hADMSCs with the transcriptional coactivator with PDZ-binding motif (TAZ) via polymer nanoparticle-mediated gene delivery. TAZ is a well-known transcriptional modulator that activates the osteogenic differentiation of mesenchymal stem cells (MSCs). Two-stage HAp-functionalized SF scaffolds significantly promoted the osteogenic differentiation of TAZ-transfected hADMSCs in vitro and enhanced mineralized bone formation in a critical-sized calvarial bone defect model. Our study shows the potential utility of SF scaffolds with nanofibrous structures and enriched inorganic components in bone tissue engineering.

Preparation and investigation of novel SrCl2/DCMC-modified (via DOPA) decellularized arteries with excellent physicochemical properties and cytocompatibility for vascular scaffolds

A new method of fabricating vascular scaffolds was designed in this article by crosslinking the porcine arteries using dialdehyde carboxymethyl (DCMC) and further introducing the Sr element on the surface of modified arteries using DOPA. DCMC had been selected as an ideal crosslinking reagent for its excellent cytobiocompatibility and suitable chemical reactivity. Unfortunately, the endothelialization of biological vascular scaffolds fixed by DCMC was unsatisfactory. To overcome this deficiency, the Sr element was introduced onto arteries to improve the endothelialization of fixed arteries due to the Sr element being able to promote the expression of vascular endothelial growth factor (VEGF) being crucial for growth and proliferation of HUVECs. After modifying and crosslinking, their chemical structures, mechanical properties, stability, and cytocompatibility were examined. Our findings demonstrated that DCMC could improve the mechanical properties of animal-derived materials successfully and possess suitable biocompatibility compared with glutaraldehyde (GA). The Sr element can easily be introduced onto the surface of DCMC modified arteries by DOPA. Compared with purely DCMC-crosslinked ones, SrCl₂/DCMC modification has no significant effect on the mechanical strength of fixed arteries, but a slight tendancy to improve the stability of fixed samples in D-Hanks solution. MTT assay and fluorescence tests implied that SrCl₂/DCMC modification could effectively stimulate HUVECs' adhesion and proliferation, and thus promote the endothelialization process of fixed arteries. SrCl₂/DCMC-modified arteries with excellent physicochemical properties and appealing HUVEC-cytocompatibility should be promising materials for fabricating vascular scaffolds.

A new method of fabricating vascular scaffolds was designed in this article by crosslinking the porcine arteries using dialdehyde carboxymethyl (DCMC) and further introducing the Sr element on the surface of modified arteries using DOPA.

Biodegradable Bisvinyl Sulfonemethyl-crosslinked Gelatin Conduit Promotes Regeneration after Peripheral Nerve Injury in Adult Rats

In our previous study, we found that gelatin-based materials exhibit good conductivity and are non-cytotoxic. In this study, gelatin was cross-linked with bisvinyl sulfonemethyl (BVSM) to fabricate a biodegradable conduit for peripheral nerve repair. First, BVSM on the prepared conduit was characterized to determine its mechanical properties and contact angle. The maximum tensile strength and water contact angle of the gelatin-BVSM conduits were 23 ± 4.8 MPa and 74.7 ± 9°, which provided sufficient mechanical strength to resist muscular contraction; additionally, the surface was hydrophilic. Cytotoxicity and apoptosis assays using Schwann cells demonstrated that the gelatin-BVSM conduits are non-cytotoxic. Next, we examined the neuronal electrophysiology, animal behavior, neuronal connectivity, macrophage infiltration, calcitonin gene-related peptide localization and expression, as well as the expression levels of nerve regeneration-related proteins. The number of fluorogold-labelled cells and histological analysis of the gelatin-BVSM nerve conduits was similar to that observed with the clinical use of silicone rubber conduits after 8 weeks of repair. Therefore, our results demonstrate that gelatin-BVSM conduits are promising substrates for application as bioengineered grafts for nerve tissue regeneration.

AgNPs-decorated 3D printed PEEK implant for infection control and bone repair

Polyetheretherketone (PEEK) is an ideal substitute material for bone tissue engineering, which can avoid the stress shielding phenomenon due to its similar mechanical properties to natural human bone. Complex bone defect and postoperative infection are still two enormous challenges in orthopedic clinics. It's well-known that additive manufacturing possesses the merits of high-precision and rapid prototyping, thus it easily meets the needs of mold processing. In the present study, we developed a novel Ag-decorated 3D printed PEEK via catecholamine chemistry. SEM image showed that silver nanoparticles (AgNPs) were evenly anchored on the surface. The following antibacterial tests, including bacterial inhibition ring, bacterial dynamics curves and antibiofilm test, indicated that the Ag-decorated 3D PEEK scaffolds displayed significant antibacterial effect towards Gram-negative and Gram-positive bacteria. Then MG-63 cells were seeded on samples for cell proliferation and ALP activity tests. The results demonstrated the scaffold modified with AgNPs could support cell proliferation, and enhanced higher alkaline phosphatase activity compared with pure PEEK scaffold. Expectedly, this dual functional 3D material holds great potential application in clinical bone tissue repair.

Time-Resolved Study of Nanomorphology and Nanomechanic Change of Early-Stage Mineralized Electrospun Poly(lactic acid) Fiber by Scanning Electron Microscopy, Raman Spectroscopy and Atomic Force Microscopy

In this study, scanning electron microscopy (SEM), Raman spectroscopy and high-resolution atomic force microscopy (AFM) were used to reveal the early-stage change of nanomorphology and nanomechanical properties of poly(lactic acid) (PLA) fibers in a time-resolved manner during the mineralization process. Electrospun PLA nanofibers were soaked in simulated body fluid (SBF) for different periods of time (0, 1, 3, 5, 7 and 21 days) at 10 °C, much lower than the conventional 37 °C, to simulate the slow biomineralization process. Time-resolved Raman spectroscopy analysis can confirm that apatites were deposited on PLA nanofibers after 21 days of mineralization. However, there is no significant signal change among several Raman spectra before 21 days. SEM images can reveal the mineral deposit on PLA nanofibers during the process of mineralization. In this work, for the first time, time-resolved AFM was used to monitor early-stage nanomorphology and nanomechanical changes of PLA nanofibers. The Surface Roughness and Young’s Modulus of the PLA nanofiber quantitatively increased with the time of mineralization. The electrospun PLA nanofibers with delicate porous structure could mimic the extracellular matrix (ECM) and serve as a model to study the early-stage mineralization. Tested by the mode of PLA nanofibers, we demonstrated that AFM technique could be developed as a potential diagnostic tool to monitor the early onset of pathologic mineralization of soft tissues.

Surface PEGylation of mesoporous silica materials via surface-initiated chain transfer free radical polymerization: Characterization and controlled drug release

As a new type of mesoporous silica materials with large pore diameter (pore size between 2 and 50nm) and high specific surface areas, SBA-15 has been widely explored for different applications especially in the biomedical fields. The surface modification of SBA-15 with functional polymers has demonstrated to be an effective way for improving its properties and performance. In this work, we reported the preparation of PEGylated SBA-15 polymer composites through surface-initiated chain transfer free radical polymerization for the first time. The thiol group was first introduced on SBA-15 via co-condensation with γ-mercaptopropyltrimethoxysilane (MPTS), that were utilized to initiate the chain transfer free radical polymerization using poly(ethylene glycol) methyl ether methacrylate (PEGMA) and itaconic acid (IA) as the monomers. The successful modification of SBA-15 with poly(PEGMA-co-IA) copolymers was evidenced by a series of characterization techniques, including ¹H NMR, FT-IR, TGA and XPS. The final SBA-15-SH- poly(PEGMA-co-IA) composites display well water dispersity and high loading capability towards cisplatin (CDDP) owing to the introduction of hydrophilic PEGMA and carboxyl groups. Furthermore, the CDDP could be released from SBA-15-SH-poly(PEGMA-co-IA)-CDDP complexes in a pH dependent behavior, suggesting the potential controlled drug delivery of SBA-15-SH-poly(PEGMA-co-IA). More importantly, the strategy should be also useful for fabrication of many other functional materials for biomedical applications owing to the advantages of SBA-15 and well monomer adoptability of chain transfer free radical polymerization.

Icariin immobilized electrospinning poly(l-lactide) fibrous membranes via polydopamine adhesive coating with enhanced cytocompatibility and osteogenic activity

In this study, icariin (ICA), one of the main active ingredients of Herba Epimedii for osteogenesis, was applied to functionalize electrospinning poly(l-lactide) (PLLA) fibrous membrane via an intermediate layer of polydopamine (PDA) to obtain enhanced cytocompatibility and osteogenic activity. For this purpose, an array of PDA-coated PLLA fibrous membranes (PLLA-0.5PDA, PLLA-1PDA, PLLA-2PDA, PLLA-5PDA) and ICA-modified PLLA-2PDA fibrous membranes (PLLA-2PDA-10ICA, PLLA-2PDA-20ICA, PLLA-2PDA-40ICA) were successively prepared. Successful modification of PDA and ICA onto PLLA fibrous membranes was verified by field emission scanning electron microscope (FESEM), thermogravimetric analysis (TGA) and X-ray photoelectron spectroscopy (XPS). Besides, the hydrophilicity as well as tensile properties of PLLA fibrous membrane were improved after surface modified with PDA and ICA. In vitro cells culture experiments revealed that the adhesion, proliferation and osteogenic differentiation of MC3T3-E1 cells on the PLLA fibrous membrane were significantly improved by successively immobilized with PDA and ICA. Moreover, the concentration of ICA immobilized on the fibrous membranes has the complicated effects on the MC3T3-E1 cells behavior. The PLLA-2PDA-ICA fibrous membranes with low ICA concentration promoted the cell adhesion and proliferation, but on the contrary, those with high ICA concentration were more beneficial to the enhancement in ALP activity and calcium deposition.

Calcium Silicate/Chitosan-Coated Electrospun Poly (Lactic Acid) Fibers for Bone Tissue Engineering

Electrospinning technology allows fabrication of nano- or microfibrous fibers with inorganic and organic matrix and it is widely applied in bone tissue engineering as it allows precise control over the shapes and structures of the fibers. Natural bone has an ordered composition of organic fibers with dispersion of inorganic apatite among them. In this study, poly (lactic acid) (PLA) mats were fabricated with electrospinning and coated with chitosan (CH)/calcium silicate (CS) mixer. The microstructure, chemical component, and contact angle of CS/CH-PLA composites were analyzed by scanning electron microscopy, X-ray diffraction, and Fourier transform infrared spectroscopy. In vitro, various CS/CH-coated PLA mats increased the formation of hydroxyapatite on the specimens' surface when soaked in cell cultured medium. During culture, several biological characteristics of the human mesenchymal stem cells (hMSCs) cultured on CS/CH-PLA groups were promoted as compared to those on pure PLA mat. Increased secretion levels of Collagen I and fibronectin were observed in calcium silicate-powder content. Furthermore, with comparison to PLA mats without CS/CH, CS10 and CS15 mats markedly enhanced the proliferation of hMSCs and their osteogenesis properties, which was characterized by osteogenic-related gene expression. These results clearly demonstrated that the biodegradable and electroactive CS/CH-PLA composite mats are an ideal and suitable candidate for bone tissue engineering.