Biocompatibility and degradation characteristics of PLGA-based electrospun nanofibrous scaffolds with nanoapatite incorporation

Biodegradable Electrospun PLGA Nanofibers-Encapsulated Trichinella Spiralis Antigens Protect from Relapsing Experimental Autoimmune Encephalomyelitis and Related Gut Microbiota Dysbiosis

Purpose

Trichinella spiralis has evolved complex immunomodulatory mechanisms mediated by excretory-secretory products (ESL1) that enable its survival in the host. Consequently, ESL1 antigens display excellent potential for treating autoimmune diseases such as multiple sclerosis (MS). However, whether timely controlled delivery of ESL1 antigens in vivo, as in natural infections, could enhance its therapeutic potential for MS is still unknown.

Methods

To test this, we encapsulated ESL1 antigens into biodegradable poly (lactide-co-glycolic) acid (PLGA) nanofibers by emulsion electrospinning as a delivery system and assessed their release dynamics in vitro, and in an animal MS model, experimental autoimmune encephalomyelitis (EAE), induced 7 days after PLGA/ESL1 subcutaneous implantation. PLGA/ESL1 effects on EAE symptoms were monitored along with multiple immune cell subsets in target organs at the peak and recovery of EAE. Gut barrier function and microbiota composition were analyzed using qPCR, 16S rRNA sequencing, and metabolomic analyses.

Results

ESL1 antigens, released from PLGA and drained via myeloid antigen-presenting cells through lymph nodes, protected the animals from developing EAE symptoms. These effects correlated with reduced activation of myeloid cells, increased IL-10 expression, and reduced accumulation of proinflammatory natural killer (NK) cells, T helper (Th)1 and Th17 cells in the spleen and central nervous system (CNS). Additionally, CD4+CD25hiFoxP3+ regulatory T cells and IL-10-producing B cells were expanded in PLGA/ESL1-treated animals, compared to control animals. The migration of ESL1 to the guts correlated with locally reduced inflammation and gut barrier damage. Additionally, PLGA/ESL1-treated animals displayed an unaltered microbiota characterized only by a more pronounced protective mevalonate pathway and expanded short-chain fatty acid-producing bacteria, which are known to suppress inflammation.

Conclusion

The delivery of T. spiralis ESL1 antigens via biodegradable electrospun PLGA nanofiber implants efficiently protected the animals from developing EAE by inducing a beneficial immune response in the spleen, gut, and CNS. This platform provides excellent grounds for further development of novel MS therapies.

Evaluation of physicochemical property changes in 3D-printed biodegradable medical devices under simulated oral physiological conditions

Biodegradable medical devices undergo degradation following implantation, potentially leading to clinical failure. Consequently, it is necessary to assess the change in their properties post-implantation. However, a standardized method for the precise evaluation of the changes in their physicochemical properties is currently lacking. In this study, we aimed to establish precisely simulated oral physiological conditions (SOPCs) and investigate the physicochemical property changes to predict the performance alterations of biodegradable dental barrier membranes (BDBMs) following human implantation. We investigated changes in physicochemical properties of BDBM after exposure to SOPC for 24 weeks. When BDBM was exposed to SOPC for 24 weeks, there was a significant decrease in mass (-1.37%), molecular weight (-19.54%) and tensile load (-72.84%). Among the physicochemical properties, molecular weight decreased similarly after 24 weeks of implantation in rats (-15.78%) and after 24 weeks of exposure to SOPC (-19.54%). Changes in the physicochemical properties of BDBM in simulatedin vitrooral conditions and in thein vivoenvironment were similar. Overall, the evaluation of physicochemical property changes after exposing BDBM to the proposed SOPC demonstrates novelty in its ability to accurately predict performance changes post-implantation. This approach may provide significant insights not only for the development of BDBM but also for various types of biodegradable medical devices.

A PLGA/Silk Fibroin Nanofibre Membrane Loaded with Natural Flavonoid Compounds Extracted from Green Cocoons for Wound Healing

The use of biodegradable materials combined with natural metabolites in wound dressings has received much attention. Flavonoids (FLs) from green cocoons, as metabolites, have antibacterial, antioxidant, anti-inflammatory, and other pharmacological effects. In this study, composite membranes of FL-loaded polylactic glycolic acid (PLGA)/silk fibroin (SF) were prepared by an electrospinning method. The prepared membranes, including SF, exhibited a good slow-release effect and cytocompatibility. An in vitro evaluation of the FL-loaded PLGA/SF membranes demonstrated good antioxidant, antibacterial, and anti-inflammatory properties. Animal experiments showed that the wound healing rate of PLGA/SF-2.5FL membranes within 15 days was 97.3%, and that of the control group was 72.5%. The PLGA/SF-2.5FL membranes shortened the inflammatory period of a full-layer wound model and promoted skin regeneration and wound healing by downregulating expression of the pro-inflammatory cytokines IL-1β and TNF-α and promoting expression of the growth factors VEGF, TGF-β, and EGF. In summary, the PLGA/SF-2.5FL composite nanofibre membrane with anti-inflammatory properties is an ideal wound dressing to promote acute wound healing.

Fabrication of a modified bacterial cellulose with different alkyl chains and its prevention of abdominal adhesion

Abdominal hernia mesh is a common product which is used for prevention of abdominal adhesion and repairing abdominal wall defect. Currently, designing and preparing a novel bio-mesh material with prevention of adhesion, promoting repair and good biocompatibility simultaneously remain a great bottleneck. In this study, a novel siloxane-modified bacterial cellulose (BC) was designed and fabricated by chemical vapor deposition silylation, then the effects of different alkyl chains length of siloxane on surface properties and cell behaviors were explored. The effect of preventing of abdominal adhesion and repairing abdominal wall defect in rats with the siloxane-modified BC was evaluated. As the grafted alkyl chains become longer, the surface of the siloxane-modified BC can be transformed from super hydrophilic to hydrophobic. In vivo results showed that BC-C16 had good long-term anti-adhesion effect, good tissue adaptability and histocompatibility, which is expected to be used as a new anti-adhesion hernia repair material in clinic.

Tracking the effects of PLGA-based nanoparticles on protein expression in living cells through quantitative proteomics

Mass spectrometry (MS)-based proteomics can identify and quantify the differential abundance of expressed proteins in parallel, and bottom-up proteomic approaches are even approaching comprehensive coverage of the complex eukaryotic proteome. Protein-nanoparticle (NP) interactions have been extensively studied owing to their importance in biological applications and nanotoxicology. However, the proteome-level effects of NPs on cells have received little attention, although changes in protein abundance can reflect the direct effects of nanocarriers on protein expression. Herein, we investigated the effect of PLGA-based NPs on protein expression in HepG2 cells using a label-free quantitative proteomics approach with data independent acquisition (DIA). The percentage of two-fold change in the protein expression of cells treated with PLGA-based NPs was less than 10.15% during a 6 hour observation period. Among the changed proteins, we found that dynamic proteins involved in cell division, localization, and transport are more likely to be more susceptible to PLGA-based NPs.

Biodegradable Electrospun Conduit with Aligned Fibers Based on Poly(lactic-co-glycolic Acid) (PLGA)/Carbon Nanotubes and Choline Bitartrate Ionic Liquid

Functionally active aligned fibers are a promising approach to enhance neuro adhesion and guide the extension of neurons for peripheral nerve regeneration. Therefore, the present study developed poly(lactic-co-glycolic acid) (PLGA)-aligned electrospun mats and investigated the synergic effect with carbon nanotubes (CNTs) and Choline Bitartrate ionic liquid (Bio-IL) on PLGA fibers. Morphology, thermal, and mechanical performances were determined as well as the hydrolytic degradation and the cytotoxicity. Results revealed that electrospun mats are composed of highly aligned fibers, and CNTs were aligned and homogeneously distributed into the fibers. Bio-IL changed thermal transition behavior, reduced glass transition temperature (Tg), and favored crystal phase formation. The mechanical properties increased in the presence of CNTs and slightly decreased in the presence of the Bio-IL. The results demonstrated a decrease in the degradation rate in the presence of CNTs, whereas the use of Bio-IL led to an increase in the degradation rate. Cytotoxicity results showed that all the electrospun mats display metabolic activity above 70%, which demonstrates that they are biocompatible. Moreover, superior biocompatibility was observed for the electrospun containing Bio-IL combined with higher amounts of CNTs, showing a high potential to be used in nerve tissue engineering.

In Vitro and In Vivo Degradation of Photo-Crosslinked Poly(Trimethylene Carbonate-co-ε-Caprolactone) Networks

Three-armed poly(trimethylene carbonate) (PTMC) and poly(trimethylene carbonate-co-Ɛ-caprolactone) (P(TMC-co-ε-CL)) macromers with molecular weights of approximately 30 kg mol-1 are synthesized by ring-opening polymerization and subsequent functionalization with methacrylic anhydride. Networks are then prepared by photo-crosslinking. To investigate the in vitro and in vivo degradation properties of these photo-crosslinked networks and assess the effect of ε-caprolactone content on the degradation properties, PTMC networks, and copolymer networks with two different TMC:ε-CL ratios are prepared. PTMC networks degraded slowly, via an enzymatic surface erosion process, both in vitro and in vivo. Networks prepared from P(TMC-co-ε-CL) macromers with a 74:26 ratio are found to degrade slowly as well, via a surface erosion process, albeit at a higher rate compared to PTMC networks. Increasing the ε-CL content to a ratio of 52:48, resulted in a faster degradation. These networks lost their mechanical properties much sooner than the other networks. Thus, PTMC and P(TMC-co-ε-CL) networks are interesting networks for tissue engineering purposes and the exact degradation properties can be tuned by varying the TMC:ε-CL ratio, providing researchers with a tool to obtain copolymer networks with the desired degradation rate depending on the intended application.

Biocompatible and antibacterial poly(lactic acid)/cellulose nanofiber‑silver nanoparticle biocomposites prepared via Pickering emulsion method

Developing biocompatible and antibacterial materials with biodegradable polymers is an ideal strategy to improve public health problems and plastic pollution simultaneously. In the present study, novel biocompatible and antibacterial poly (L-lactic acid) (PLLA, coded as P)/TEMPO-oxidized cellulose nanofiber (TOCNF, coded as T)‑silver nanoparticle (AgNP, coded as A) films were first developed. The core/shell PT Pickering emulsion was prepared by sonication treatment. The TOCNF shells with -COO-Na+ groups (∼1.5 mmol/g cellulose) were used as the support to in situ synthesize and immobilize AgNPs on the PT emulsion droplets. Silver nitrate (AgNO3) (1.5, 3.0, 4.5, and 6.0 mmol/g cellulose) was added to the PT emulsions. Then, ion-exchange reaction and hydrothermal reduction were conducted to form PTA (PTA1-PTA4) emulsions. After centrifugation to remove the excess Ag+, filtration, oven-drying, and hot-pressing, the PTA composite films were successfully prepared. The PTA3 film contained AgNPs 12.4 ± 2.8 nm in diameter and exhibited the highest antibacterial activities against the E. coli (85.2%) and S. aureus (80.1%) at 37 °C, where the initial bacterial suspension concentrations were approximately 2 × 108 CFU mL-1. Therefore, the biocompatible and antibacterial PTA3 film is a promising candidate for biomedical applications, in particular as an antibacterial bioactive packaging material.

In Vivo Evaluation of Bone Regenerative Capacity of the Novel Nanobiomaterial: β-Tricalcium Phosphate Polylactic Acid-co-Glycolide (β-TCP/PLLA/PGA) for Use in Maxillofacial Bone Defects

Maxillofacial bone defects are treated by autografting or filling with synthetic materials in various forms and shapes. Electrospun nanobiomaterials are becoming popular due to their easy placement and handling; combining ideal biomaterials extrapolates better outcomes. We used a novel electrospun cotton-like fiber made from two time-tested bioresorbable materials, β-TCP and PLLA/PGA, to check the feasibility of its application to maxillofacial bone defects through an in vivo rat mandibular bone defect model. Novel β-TCP/PLLA/PGA and pure β-TCP blocks were evaluated for new bone regeneration through assessment of bone volume, inner defect diameter reduction, and bone mineral density. Bioactive/osteoconductivity was checked by scoring the levels of Runt-related transcription factor x, Leptin Receptor, Osteocalcin, and Periostin biomarkers. Bone regeneration in both β-TCP/PLLA/PGA and β-TCP was comparable at initial timepoints. Osteogenic cell accumulation was greater in β-TCP/PLLA/PGA than in β-TCP at initial as well as late phases. Periostin expression was more marked in β-TCP/PLLA/PGA. This study demonstrated comparable results between β-TCP/PLLA/PGA and β-TCP in terms of bone regeneration and bioactivity, even with a small material volume of β-TCP/PLLA/PGA and a decreased percentage of β-TCP. Electrospun β-TCP/PLLA/PGA is an ideal nanobiomaterial for inducing bone regeneration through osteoconductivity and bioresorbability in bony defects of the maxillofacial region.

Injectable pulverized electrospun poly(lactic-co-glycolic acid) fibers improve human adipose tissue engraftment and volume retention

Autologous adipose tissue is commonly used for tissue engraftment for the purposes of soft tissue reconstruction due to its relative abundance in the human body and ease of acquisition using liposuction methods. This has led to the adoption of autologous adipose engraftment procedures that allow for the injection of adipose tissues to be used as a "filler" for correcting cosmetic defects and deformities in soft tissues. However, the clinical use of such methods has several limitations, including high resorption rates and poor cell survivability, which lead to low graft volume retention and inconsistent outcomes. Here, we describe a novel application of milled electrospun poly(lactic-co-glycolic acid) (PLGA) fibers, which can be co-injected with adipose tissue to improve engraftment outcomes. These PLGA fibers had no significant negative impact on the viability of adipocytes in vitro and did not elicit long-term proinflammatory responses in vivo. Furthermore, co-delivery of human adipose tissue with pulverized electrospun PLGA fibers led to significant improvements in reperfusion, vascularity, and retention of graft volume compared to injections of adipose tissue alone. Taken together, the use of milled electrospun fibers to enhance autologous adipose engraftment techniques represents a novel approach for improving upon the shortcomings of such methods.

Tissue engineered skin substitutes: A comprehensive review of basic design, fabrication using 3D printing, recent advances and challenges

The multi-layered skin structure includes the epidermis, dermis and hypodermis, which forms a sophisticated tissue composed of extracellular matrix (ECM). The wound repair is a well-orchestrated process when the skin is injured. However, this natural wound repair will be ineffective for large surface area wounds. Autografts-based treatment is efficient but, additional pain and secondary healing of the patient limits its successful application. Therefore, there is a substantial need for fabricating tissue-engineered skin constructs. The development of a successful skin graft requires a fundamental understanding of the natural skin and its healing process, as well as design criteria for selecting a biopolymer and an appropriate fabrication technique. Further, the fabrication of an appropriate skin graft needs to meet physicochemical, mechanical, and biological properties equivalent to the natural skin. Advanced 3D bioprinting provides spatial control of the placement of functional components, such as biopolymers with living cells, which can satisfy the prerequisites for the preparation of an ideal skin graft. In this view, here we elaborate on the basic design requirements, constraints involved in the fabrication of skin graft and choice of ink, the probable solution by 3D bioprinting technique, as well as their latest advancements, challenges, and prospects.

Poly (l-lactic acid)-based modified nanofibrous membrane with dual drug release capability for GBR application

Electrospun multilayer nanofibers guided bone regeneration (GBR) with a new design were developed in this study. The synthesized multilayer GBR was composed of two distinct layers. Poly l-lactic acid (PLA) incorporated with simvastatin (SIM) was designed as PLA/SIM layer to contact with a bone defect. In addition, the hydrophilic gelatin (GT) containing thymol (THY) was fabricated as GT/THY layer to contact connective tissue, potentially for bacterial gathering. Due to the different chemical nature and weak cohesion of the hydrophilic and hydrophobic layers, hybrid fibers made of PLA/SIM and GT/THY were electrospun as cohesion promoters between these layers. The microstructure and characteristics of the synthesized multilayer substrate, named GT/PLA, were evaluated, and different fibrous monolayers were fabricated to determine the optimal concentrations of drugs. Scanning electron microscopy (SEM) images showed continuous, smooth, randomly aligned, and bead-free fibers. In addition, there were no drug particles on the fiber surfaces which displayed the good placement of those inside the fibers. The mats exhibited satisfactory tensile strength (4.60 ± 0.14 MPa) and favorable physicochemical properties, including proper porosity percentage (<50 %) and appropriate pore size. Suitable swelling behavior (293 ± 0.05 %) and adequate degradation rates were also approved by characterizing swelling and degradability in vitro. The GT/PLA membrane exhibited a prolonged and sustained SIM release and controlled THY release with high antibacterial efficiency. Cell viability, cell attachment assay, and nuclear staining using 4',6-diamidino-2-phenylindole (DAPI) showed that the designed GT/PLA substrate had good biocompatibility and cell attachment. Cell infiltration testing also showed that the cells were finely prevented by the outer layer (GT/THY). Overall, the obtained results in this study indicated the great potential of the prepared GT/PLA for use as a GBR which can develop osteogenic and antibacterial biomimetic periosteum optimizing the clinical application of GBR strategies.

Multi-modulation of immune-inflammatory response using bioactive molecule-integrated PLGA composite for spinal fusion

Despite current developments in bone substitute technology for spinal fusion, there is a lack of adequate materials for bone regeneration in clinical applications. Recombinant human bone morphogenetic protein-2 (rhBMP-2) is commercially available, but a severe inflammatory response is a known side effect. Bone graft substitutes that enhance osteogenesis without adverse effects are needed. We developed a bioactive molecule-laden PLGA composite with multi-modulation for bone fusion. This bioresorbable composite scaffold was considered for bone tissue engineering. Among the main components, magnesium hydroxide (MH) aids in reduction of acute inflammation affecting disruption of new bone formation. Decellularized bone extracellular matrix (bECM) and demineralized bone matrix (DBM) composites were used for osteoconductive and osteoinductive activities. A bioactive molecule, polydeoxyribonucleotide (PDRN, PN), derived from trout was used for angiogenesis during bone regeneration. A nano-emulsion method that included Span 80 was used to fabricate bioactive PLGA-MH-bECM/DBM-PDRN (PME2/PN) composite to obtain a highly effective and safe scaffold. The synergistic effect provided by PME2/PN improved not only osteogenic and angiogenic gene expression for bone fusion but also improved immunosuppression and polarization of macrophages that were important for bone tissue repair, using a rat model of posterolateral spinal fusion (PLF). It thus had sufficient biocompatibility and bioactivity for spinal fusion.

Promotion of In Vitro Osteogenic Activity by Melt Extrusion-Based PLLA/PCL/PHBV Scaffolds Enriched with Nano-Hydroxyapatite and Strontium Substituted Nano-Hydroxyapatite

Bone tissue engineering has emerged as a promising strategy to overcome the limitations of current treatments for bone-related disorders, but the trade-off between mechanical properties and bioactivity remains a concern for many polymeric materials. To address this need, novel polymeric blends of poly-L-lactic acid (PLLA), polycaprolactone (PCL) and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) have been explored. Blend filaments comprising PLLA/PCL/PHBV at a ratio of 90/5/5 wt% have been prepared using twin-screw extrusion. The PLLA/PCL/PHBV blends were enriched with nano-hydroxyapatite (nano-HA) and strontium-substituted nano-HA (Sr-nano-HA) to produce composite filaments. Three-dimensional scaffolds were printed by fused deposition modelling from PLLA/PCL/PHBV blend and composite filaments and evaluated mechanically and biologically for their capacity to support bone formation in vitro. The composite scaffolds had a mean porosity of 40%, mean pores of 800 µm, and an average compressive modulus of 32 MPa. Polymer blend and enriched scaffolds supported cell attachment and proliferation. The alkaline phosphatase activity and calcium production were significantly higher in composite scaffolds compared to the blends. These findings demonstrate that thermoplastic polyesters (PLLA and PCL) can be combined with polymers produced via a bacterial route (PHBV) to produce polymer blends with excellent biocompatibility, providing additional options for polymer blend optimization. The enrichment of the blend with nano-HA and Sr-nano-HA powders enhanced the osteogenic potential in vitro.

Physico-mechanical and in-vivo evaluations of tri-layered alginate-gelatin/polycaprolactone-gelatin-β-TCP membranes for guided bone regeneration

Guided bone regeneration (GBR) membranes favor periodontal regrowth, but they still have certain limitations, such as improper biodegradation and poor mechanical property. To overcome these shortcomings, we have generated a unique multifunctional membrane. A polycaprolactone/gelatin/β-TCP and alginate/gelatin trilayered construction was fabricated through electrospinning and casting technology. The prepared membranes have suitable physicomechanical and in-vitro properties to confirm the compatibility of the product in the body. Phase analysis, functional groups, surface microstructure, and contact angle were measured as basic characteristics. For a mechanical performance evaluation, the tensile strength at suturing point was measured through pullout tensile strength test, and it showed the suture capability of bi-layered membranes. Highest tensile strength for A75G25 was recorded with 2.9 ± 0.15 MPa with 105% strain. Further, the osteoblast and fibroblast-type cell toxicity results showed that the electrospun membrane offered compatible environment to cells while the alginate sheet was found to be sufficiently capable to suppress the cellular attachment while also being a nontoxic material. Post-implantation, according to the in-vivo conclusions of the tri-layered membrane, there was appreciable bone formation. Compared to an implant without membrane covering, enhanced new bone formation can be identified after 8 weeks of implantation with P1G4β10 membranes-covered site.

Monitoring the Remodeling of Biohybrid Tissue-Engineered Vascular Grafts by Multimodal Molecular Imaging

Tissue-engineered vascular grafts (TEVGs) with the ability to grow and remodel open new perspectives for cardiovascular surgery. Equipping TEVGs with synthetic polymers and biological components provides a good compromise between high structural stability and biological adaptability. However, imaging approaches to control grafts' structural integrity, physiological function, and remodeling during the entire transition between late in vitro maturation and early in vivo engraftment are mandatory for clinical implementation. Thus, a comprehensive molecular imaging concept using magnetic resonance imaging (MRI) and ultrasound (US) to monitor textile scaffold resorption, extracellular matrix (ECM) remodeling, and endothelial integrity in TEVGs is presented here. Superparamagnetic iron-oxide nanoparticles (SPION) incorporated in biodegradable poly(lactic-co-glycolic acid) (PLGA) fibers of the TEVGs allow to quantitatively monitor scaffold resorption via MRI both in vitro and in vivo. Additionally, ECM formation can be depicted by molecular MRI using elastin- and collagen-targeted probes. Finally, molecular US of αv β3 integrins confirms the absence of endothelial dysfunction; the latter is provocable by TNF-α. In conclusion, the successful employment of noninvasive molecular imaging to longitudinally evaluate TEVGs remodeling is demonstrated. This approach may foster its translation from in vitro quality control assessment to in vivo applications to ensure proper prostheses engraftment.

The Biodegradability and in Vitro Cytological Study on the Composite of PLGA Combined With Magnesium Metal

The main goal of this study was to develop a novel poly (lactic-co-glycolic acid) (PLGA) composite biodegradable material with magnesium (Mg) metal to overcome the acidic degradation of PLGA and to investigate the cytocompatibility and osteogenesis of the novel material. PLGA composites with 5 and 10 wt% Mg were prepared. The samples were initially cut into 10 mm × 10 mm films, which were used to detect the pH value to evaluate the self-neutralized ability. Murine embryo osteoblast precursor (MC3T3-E1) cells were used for in vitro experiments to evaluate the cytotoxicity, apoptosis, adhesion, and osteogenic differentiation effect of the composite biodegradable material. pH monitoring showed that the average value of PLGA with 10 wt% Mg group was closer to the normal physiological environment than that of other groups. Cell proliferation and adhesion assays indicated no significant difference between the groups, and all the samples showed no toxicity to cells. As for cell apoptosis detection, the rate of early apoptotic cells was proportional to the ratio of Mg. However, the ratios of the experimental groups were lower than those of the control group. Alkaline phosphatase activity staining demonstrated that PLGA with 10 wt% Mg could effectively improve the osteogenic differentiation of MC3T3-E1 cells. In summary, PLGA with 10 wt% Mg possessed effective osteogenic properties and cytocompatibility and therefore could provide a wide range of applications in bone defect repair and scaffold-based tissue engineering in clinical practice.

Genipin-Crosslinked, Proteosaccharide Scaffolds for Potential Neural Tissue Engineering Applications

Traumatic brain injuries (TBIs) are still a challenge for the field of modern medicine. Many treatment options such as autologous grafts and stem cells show limited promise for the treatment and the reversibility of damage caused by TBIs. Injury beyond the critical size necessitates the implementation of scaffolds that function as surrogate extracellular matrices. Two scaffolds were synthesised utilising polysaccharides, chitosan and hyaluronic acid in conjunction with gelatin. Both scaffolds were chemically crosslinked using a naturally derived crosslinker, Genipin. The polysaccharides increased the mechanical strength of each scaffold, while gelatin provided the bioactive sequence, which promoted cellular interactions. The effect of crosslinking was investigated, and the crosslinked hydrogels showed higher thermal decomposition temperatures, increased resistance to degradation, and pore sizes ranging from 72.789 ± 16.85 µm for the full interpenetrating polymer networks (IPNs) and 84.289 ± 7.658 μm for the semi-IPN. The scaffolds were loaded with Dexamethasone-21-phosphate to investigate their efficacy as a drug delivery vehicle, and the full IPN showed a 100% release in 10 days, while the semi-IPN showed a burst release in 6 h. Both scaffolds stimulated the proliferation of rat pheochromocytoma (PC12) and human glioblastoma multiforme (A172) cell cultures and also provided signals for A172 cell migration. Both scaffolds can be used as potential drug delivery vehicles and as artificial extracellular matrices for potential neural regeneration.

Amniotic Epithelial Stem Cells Counteract Acidic Degradation By-Products of Electrospun PLGA Scaffold by Improving Their Immunomodulatory Profile In Vitro

Electrospun poly(lactic-co-glycolic acid) (PLGA) scaffolds with highly aligned fibers (ha-PLGA) represent promising materials in the field of tendon tissue engineering (TE) due to their characteristics in mimicking fibrous extracellular matrix (ECM) of tendon native tissue. Among these properties, scaffold biodegradability must be controlled allowing its replacement by a neo-formed native tendon tissue in a controlled manner. In this study, ha-PLGA were subjected to hydrolytic degradation up to 20 weeks, under di-H₂O and PBS conditions according to ISO 10993-13:2010. These were then characterized for their physical, morphological, and mechanical features. In vitro cytotoxicity tests were conducted on ovine amniotic epithelial stem cells (oAECs), up to 7 days, to assess the effect of non-buffered and buffered PLGA by-products at different concentrations on cell viability and their stimuli on oAECs’ immunomodulatory properties. The ha-PLGA scaffolds degraded slowly as evidenced by a slight decrease in mass loss (14%) and average molecular weight (35%), with estimated degradation half-time of about 40 weeks under di-H₂O. The ultrastructure morphology of the scaffolds showed no significant fiber degradation even after 20 weeks, but alteration of fiber alignment was already evident at week 1. Moreover, mechanical properties decreased throughout the degradation times under wet as well as dry PBS conditions. The influence of acid degradation media on oAECs was dose-dependent, with a considerable effect at 7 days’ culture point. This effect was notably reduced by using buffered media. To a certain level, cells were able to compensate the generated inflammation-like microenvironment by upregulating IL-10 gene expression and favoring an anti-inflammatory rather than pro-inflammatory response. These in vitro results are essential to better understand the degradation behavior of ha-PLGA in vivo and the effect of their degradation by-products on affecting cell performance. Indeed, buffering the degradation milieu could represent a promising strategy to balance scaffold degradation. These findings give good hope with reference to the in vivo condition characterized by physiological buffering systems.

Collagen-based biocomposites inspired by bone hierarchical structures for advanced bone regeneration: ongoing research and perspectives

Bone is a hard-connective tissue composed of matrix, cells and bioactive factors with a hierarchical structure, where the matrix is mainly composed of type I collagen and hydroxyapatite. Collagen fibers assembled by collagen are the template for mineralization and make an important contribution to bone formation and the bone remodeling process. Therefore, collagen has been widely clinically used for bone/cartilage defect regeneration. However, pure collagen implants, such as collagen scaffolds or sponges, have limitations in the bone/cartilage regeneration process due to their poor mechanical properties and osteoinductivity. Different forms of collagen-based composites prepared by incorporating natural/artificial polymers or bioactive inorganic substances are characterized by their interconnected porous structure and promoting cell adhesion, while they improve the mechanical strength, structural stability and osteogenic activities of the collagen matrix. In this review, various forms of collagen-based biocomposites, such as scaffolds, sponges, microspheres/nanoparticles, films and microfibers/nanofibers prepared by natural/synthetic polymers, bioactive ceramics and carbon-based materials compounded with collagen are reviewed. In addition, the application of collagen-based biocomposites as cytokine, cell or drug (genes, proteins, peptides and chemosynthetic) delivery platforms for proangiogenesis and bone/cartilage tissue regeneration is also discussed. Finally, the potential application, research and development direction of collagen-based biocomposites in future bone/cartilage tissue regeneration are discussed.

The Anti-Inflammation and Anti-Nociception Effect of Ketoprofen in Rats Could Be Strengthened Through Co-Delivery of a H2S Donor, S-Propargyl-Cysteine

PURPOSE

Ketoprofen (KETO) is a traditional non-steroidal anti-inflammatory drug (NSAIDs) with good analgesic and antipyretic effects. However, as NASIDs, the toxicity of KETO towards gastrointestinal (GI) system might limit its clinical use. S-propargyl-cysteine (SPRC) is an excellent endogenous H2S donor showed wide application in the field of anti-inflammation, anti-oxidative stress, or even the protection of cardiovascular system through the elevation of endogenous H2S concentration. As recently studies reported, co-administration of H2S donor might potentially mitigate the GI toxicity and relevant side effects induced by series of NSAIDs.

METHODS

In this study, we established a SPRC and KETO co-encapsulated poly (lactic-co-glycolic acid) microsphere (SK@MS), and its particle size, morphology, storage stability and in vitro release profile were firstly investigated. The elevation of endogenous H2S level of SK@MS was then calculated, and the pharmacodynamic study (anti-inflammation and analgesic effects) of SK@MS, SPRC, and KETO towards adjuvant induced arthritis (AIA) in rats were also studied. Finally, to test the potential side effect, the heart, liver, spleen, lung, kidney, stomach, small intestine, and large intestine were resected from rats and examined by H&E staining.

RESULTS

A monodispersed SK@MS could be observed under the SEM, and particle size was calculated around 25.12 μm. The loading efficiency (LE) for SPRC and KETO were 6.67% and 2.64%, respectively, while the encapsulation efficiency (EE) for SPRC and KETO were 37.20% and 68.28%, respectively. SK@MS showed a sustained release of SPRC and KETO in vitro, which was up-to 15 days. SK@MS could achieve a long-term elevation of the H2S concentration in vivo, while SPRC showed an instant H2S elevation and metabolize within 6 h. Interestingly, the KETO did not show any influence on the H2S concentration in vivo. After establishment of AIA model, neither SPRC nor KETO showed scarcely anti-inflammation and anti-nociception effect, while conversely, SK@MS showed an obvious mitigation towards paw edema and pain in AIA rats, which indicated an improved anti-inflammation and anti-nociception effect when co-delivery of SRC and KETO. Besides, low stimulation towards major organs in rats observed in any experimental group.

CONCLUSION

A monodispersed was successfully prepared in this study, and SK@MS showed a sustained SPRC and KETO release in vitro and H2S release in vivo. In the pharmacodynamics study, SK@MS not only exhibited an excellent anti-inflammation and analgesic effects in AIA rats but also showed low stimulation towards rats.

A baicalin-loaded coaxial nanofiber scaffold regulated inflammation and osteoclast differentiation for vascularized bone regeneration

We demonstrate a simple, effective and feasible method to address the shrinkage of Poly (lactic-co-glycolic acid) (PLGA) through a core-shell structure fiber strategy. The results revealed that introducing size-stable poly-caprolactone (PCL) as the core fiber significantly improved the PLGA-based fibrous scaffold's dimensional maintenance. We further utilized fish collagen to modify the PLGA shell layer (PFC) of coaxial fibers and loaded baicalin (BA) into the PCL core layer (PCL-BA) to endow fibrous scaffold with more functional biological cues. The PFC/PCL-BA fibrous scaffold promoted the osteogenic differentiation of bone mesenchymal stem cells and stimulated the RAW264.7 cells to polarize into a pro-reparative phenotype. Importantly, the in vivo study demonstrated that the PFC/PCL-BA scaffold could regulate inflammation and osteoclast differentiation, favor neovascularization and bone formation. This work tactfully combined PLGA and PCL to establish a drug release platform based on the core-shell fibrous scaffold for vascularized bone regeneration.

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A multifunctional baicalin-loaded coaxial fiber scaffold prepared by electrospinning.

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The coaxial nanofiber can effectively resist the shrinkage of PLGA.

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Baicalin endow the nanofibrous scaffold with excellent biological properties.

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The scaffold can alleviate the inflammation and achieve vascularized bone regeneration.

Optimization of Layered Dissolving Microneedle for Sustained Drug Delivery Using Heat-Melted Poly(Lactic-Co-glycolic Acid)

Dissolving microneedles (DMNs) have been used as an alternative drug delivery system to deliver therapeutics across the skin barrier in a painless manner. In this study, we propose a novel heat-melting method for the fabrication of hydrophobic poly(lactic-co-glycolic acid) (PLGA) DMNs, without the use of potentially harmful organic solvents. The drug-loaded PLGA mixture, which consisted of a middle layer of the DMN, was optimized and successfully implanted into ex vivo porcine skin. Implanted HMP-DMNs separated from the patch within 10 min, enhancing user compliance, and the encapsulated molecules were released for nearly 4 weeks thereafter. In conclusion, the geometry of HMP-DMNs was successfully optimized for safe and effective transdermal sustained drug delivery without the use of organic solvents. This study provides a strategy for the innovative utilization of PLGA as a material for transdermal drug delivery systems.

Indwelling urinary catheter assembled with lidocaine-loaded polymeric strand for local sustained alleviation of bladder discomfort

Indwelling urinary catheters (IUCs) are used in clinical settings to assist detrusor contraction in hospitalized patients. However, an inserted IUC often causes catheter-related bladder discomfort. To resolve this, we propose an IUC coupled with local, sustained release of an anesthetic drug, lidocaine. For this, a thin strand composed of poly (lactic-co-glycolic acid) and lidocaine was separately prepared as a drug delivery carrier, which was then wound around the surface of the IUC to produce the drug-delivery IUC. Our results revealed that the drug-delivery IUC could exert the pain-relief effects for up to 7 days when placed in the bladder of living rats. Cystometrogram tests indicated that the drug-delivery IUC could significantly relieve bladder discomfort compared with the IUC without lidocaine. Furthermore, the expression of pain-related inflammatory markers, such as nerve growth factor, cyclooxygenase-2, and interleukin-6 in the biopsied bladder tissues was significantly lower when the drug-delivery IUC was used. Therefore, we conclude that an IUC simply assembled with a drug-loaded polymer strand can continuously release lidocaine to allow for the relief of bladder discomfort during the period of IUC insertion.

PLGA Microspheres Containing Hydrophobically Modified Magnesium Hydroxide Particles for Acid Neutralization-Mediated Anti-Inflammation

BACKGROUND

Poly(lactic-co-glycolic acid) (PLGA) microspheres have been actively used in various pharmaceutical formulations because they can sustain active pharmaceutical ingredient release and are easy to administer into the body using a syringe. However, the acidic byproducts produced by the decomposition of PLGA cause inflammatory reactions in surrounding tissues, limiting biocompatibility. Magnesium hydroxide (MH), an alkaline ceramic, has attracted attention as a potential additive because it has an acid-neutralizing effect.

METHODS

To improve the encapsulation efficiency of hydrophilic MH, the MH particles were capped with hydrophobic ricinoleic acid (RA-MH). PLGA microspheres encapsulated with RA-MH particles were manufactured by the O/W method. To assess the in vitro cytotoxicity of the degradation products of PLGA, MH/PLGA, and RA-MH/PLGA microspheres, CCK-8 and Live/Dead assays were performed with NIH-3T3 cells treated with different concentrations of their degradation products. In vitro anti-inflammatory effect of RA-MH/PLGA microspheres was evaluated with quantitative measurement of pro-inflammatory cytokines.

RESULTS

The synthesized RA-MH was encapsulated in PLGA microspheres and displayed more than four times higher loading content than pristine MH. The PLGA microspheres encapsulated with RA-MH had an acid-neutralizing effect better than that of the control group. In an in vitro cell experiment, the degradation products obtained from RA-MH/PLGA microspheres exhibited higher biocompatibility than the degradation products obtained from PLGA microspheres. Additionally, the RA-MH/PLGA microsphere group showed an excellent anti-inflammatory effect.

CONCLUSION

Our results proved that RA-MH-encapsulated PLGA microspheres showed excellent biocompatibility with an anti-inflammatory effect. This technology can be applied to drug delivery and tissue engineering to treat various incurable diseases in the future.

Exploration of Bioengineered Scaffolds Composed of Thermo-Responsive Polymers for Drug Delivery in Wound Healing

Innate and adaptive immune responses lead to wound healing by regulating a complex series of events promoting cellular cross-talk. An inflammatory response is presented with its characteristic clinical symptoms: heat, pain, redness, and swelling. Some smart thermo-responsive polymers like chitosan, polyvinylpyrrolidone, alginate, and poly(ε-caprolactone) can be used to create biocompatible and biodegradable scaffolds. These processed thermo-responsive biomaterials possess 3D architectures similar to human structures, providing physical support for cell growth and tissue regeneration. Furthermore, these structures are used as novel drug delivery systems. Locally heated tumors above the polymer lower the critical solution temperature and can induce its conversion into a hydrophobic form by an entropy-driven process, enhancing drug release. When the thermal stimulus is gone, drug release is reduced due to the swelling of the material. As a result, these systems can contribute to the wound healing process in accelerating tissue healing, avoiding large scar tissue, regulating the inflammatory response, and protecting from bacterial infections. This paper integrates the relevant reported contributions of bioengineered scaffolds composed of smart thermo-responsive polymers for drug delivery applications in wound healing. Therefore, we present a comprehensive review that aims to demonstrate these systems' capacity to provide spatially and temporally controlled release strategies for one or more drugs used in wound healing. In this sense, the novel manufacturing techniques of 3D printing and electrospinning are explored for the tuning of their physicochemical properties to adjust therapies according to patient convenience and reduce drug toxicity and side effects.

Microsphere antioxidant and sustained erythropoietin-R76E release functions cooperate to reduce traumatic optic neuropathy

Wild-type erythropoietin (EPO) is promising for neuroprotection, but its therapeutic use is limited because it causes a systemic rise in hematocrit. We have developed an EPO-R76E derivative that maintains neuroprotective function without effects on hematocrit, but this protein has a short half-life in vivo. Here, we compare the efficacy and carrier-induced inflammatory response of two polymeric microparticle (MP) EPO-R76E sustained release formulations based on conventional hydrolytically degradable poly(lactic-co-glycolic acid) (PLGA) and reactive oxygen species (ROS)-degradable poly(propylene sulfide) (PPS). Both MP types effectively loaded EPO-R76E and achieved sustained release, providing detectable levels of EPO-R76E at the injection site in the eye in vivo for at least 28 days. Testing in an in vitro oxidative stress assay and a mouse model of blast-induced indirect traumatic optic neuropathy (bITON) showed that PPS and PLGA MP-mediated delivery of EPO-R76E provided therapeutic protection. While unloaded PLGA MPs inherently increase levels of pro-inflammatory cytokines in the bITON model, drug-free PPS MPs have innate antioxidant properties that provide therapeutic benefit both in vitro and in vivo. Both PLGA and PPS MPs enabled sustained release of EPO-R76E, providing therapeutic benefits including reduction in inflammation and axon degeneration, and preservation of visual function as measured by electroretinogram. The PPS-based MP platform is especially promising for further development, as the delivery system provides inherent antioxidant benefits that can be harnessed to work in complement with EPO-R76E or other drugs for neuroprotection in the setting of traumatic eye injury.

Biocompatibility analysis of PLA based candidate materials for cardiovascular stents in a rat subcutaneous implant model

Modification of Polylactic acid (PLA), a biopolymer, is a strategy still to be fully explored for the next generation of bioresorbable vascular stent (BVS) biomaterials. With this focus, inclusions upto 5% of Polycaprolactone (PCL) and Magnesium in PLA were tested in the rat subcutaneous model and their cellular and tissue interactions characterized, specifically with respect to inflammatory response, angiogenesis and capsularization. The cytokines IL6, TNF Alpha and IL-1Beta were estimated in the peri-implant tissue, all of which showed a non-significant difference between the non-implanted animals and those containing PLA by 8 weeks, speaking to the benign nature of PLA as an implant biomaterial. Both modified materials, had increased macrophage counts and cytokine levels, except IL6 at 8 weeks. Vascularization only at 8 weeks in PLA PCL containing tissue was significantly higher than pure PLA, which may be more carefully controlled along with the material hydrophobicity for possible efforts towards therapeutic angiogenesis. Capsule thickness, measured by staining with both Hematoxylin & Eosin and Masson's Trichome did not show any differences between materials, including PLA.

3D printing of multilayered scaffolds for rotator cuff tendon regeneration

Repairing massive rotator cuff tendon defects remains a challenge due to the high retear rate after surgical intervention. 3D printing has emerged as a promising technique that enables the fabrication of engineered tissues with heterogeneous structures and mechanical properties, as well as controllable microenvironments for tendon regeneration. In this study, we developed a new strategy for rotator cuff tendon repair by combining a 3D printed scaffold of polylactic-co-glycolic acid (PLGA) with cell-laden collagen-fibrin hydrogels. We designed and fabricated two types of scaffolds: one featuring a separate layer-by-layer structure and another with a tri-layered structure as a whole. Uniaxial tensile tests showed that both types of scaffolds had improved mechanical properties compared to single-layered PLGA scaffolds. The printed scaffold with collagen-fibrin hydrogels effectively supported the growth, proliferation, and tenogenic differentiation of human adipose-derived mesenchymal stem cells. Subcutaneous implantation of the multilayered scaffolds demonstrated their excellent in vivo biocompatibility. This study demonstrates the feasibility of 3D printing multilayered scaffolds for application in rotator cuff tendon regeneration.

A new method for the preparation of three-layer vascular stents: a preliminary study on the preparation of biomimetic three-layer vascular stents using a three-stage electrospun membrane

There is an urgent need to design a tissue-engineered vascular graft that exhibits good biocompatibility and sufficient mechanical strength to repair and facilitate regeneration of defective vascular tissue. It is generally accepted that multi-layer stents can be used to simulate the structure and function of natural blood vessels. Here, we developed a new three-layer tubular graft that is rolled from a single Poly(L-lactide-co-caprolactone) electrospun membrane. We used a new electrospinning technique to place three different structures on a single electrospun membrane such that the stent is comprised of three different layers. The inner layer is dense and suitable for endothelial cell growth, the middle layer is a parallel loose structure suitable for smooth muscle cell growth, and the outer layer is a parallel structure with sparse alternating texture suitable for both smooth muscle cell growth and structural support. The vascular stent has good tensile strength. At the same time, endothelial cells and smooth muscle cells readily proliferate on the material in vitro. In particular, smooth muscle cells grow in parallel on the middle and outer materials. In vivo, all layers of the vascular graft were infiltrated by cells within one week of subcutaneous implantation, indicative of favorable biocompatibility. After a week of subcutaneous implantation, the vascular stent was orthotopically transplanted into the abdominal aorta of Sprague Dawley rats. After ten weeks of transplantation, ultrasound imaging of the abdomen showed vascular patency. The vascular stent was endothelialized, smooth muscle cells readily proliferated, and a large amount of elastic fibers were formed. Therefore, our specially designed tri-layer vascular graft may be of significant benefit in vascular reconstruction.

Revealing the Effects of Microarc Oxidation on the Mechanical and Degradation Properties of Mg-Based Biodegradable Composites

To overcome the inherent weakness of polylactic acid (PLA), used as scaffolding materials, multiple samples of Mg/PLA alloy composite materials was made by plastic injection molding. To enhance the interfacial interaction with PLA, magnesium alloy was treated with microarc oxidation (MAO) at four different frequencies, resulting in an improvement in mechanical strength and toughness. The microarc oxidation films consisted mainly of a porous MgO ceramic layer on the Mg rod. Based on the phenomenon of micro-anchoring and electrostatic interaction, a change in frequency during MAO showed considerable improvements in the ductility of the composite materials. The presence of the ceramic layer enriched the interfacial bonding between the Mg rod and outer PLA cladding, resulting in the PLA-clad Mg rod showing a higher tensile strength. In vitro degradation test was carried out in Hank's solution for different time periods. Surface-treated Mg alloy-based composite samples displayed a lower degradation rate as compared to untreated Mg alloy samples. The surface-treated sample at a 800 Hz pulse frequency showed the best degradation resistance and mechanical properties after being immersed in Hank's solution as compared to other samples. Mg-reinforced PLA composite rods are promising candidates for orthopedic implants.

Antibacterial and cytocompatible coatings based on poly(adipic anhydride) for a Ti alloy surface

This paper describes a formation of hybrid coatings on a Ti–2Ta–3Zr–36Nb surface. This is accomplished by plasma electrolytic oxidation and a dip-coating technique with poly(adipic anhydride) ((C₆H₈O₃)n) that is loaded with drugs: amoxicillin (C₁₆H₁₉N₃O₅S), cefazolin (C₁₄H₁₄N₈O₄S₃) or vancomycin (C₆₆H₇₅Cl₂N₉O₂₄ · xHCl). The characteristic microstructure of the polymer was evaluated using scanning electron microscopy and confocal microscopy. Depending on the surface treatment, the surface roughness varied (between 1.53 μm and 2.06 μm), and the wettability was change with the over of time. X-ray photoelectron spectroscopy analysis showed that the oxide layer did not affect the polymer layer or loaded drugs. However, the drugs lose their stability in a phosphate-buffered saline solution after 6.5 h of exposure, and its decrease was greater than 7% (HPLC analysis). The stability, drug release and concentration of the drug loaded into the material were precisely analyzed by high-performance liquid chromatography. The results correlated with the degradation of the polymer in which the addition of drugs caused the percent of degraded polymer to be between 35.5% and 49.4% after 1 h of material immersion, depending on the mass of the loaded drug and various biological responses that were obtained. However, all of the coatings were cytocompatible with MG-63 osteoblast-like cells. The drug concentrations released from the coatings were sufficient to inhibit adhesion of reference and clinical bacterial strains (S. aureus). The coatings with amoxicillin showed the best results in the bacterial inhibition zone, whereas coatings with cefazolin inhibited adhesion of the above bacteria on the surface.

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Hybrid layers containing fast degradable poly(adipic anhydride) (PADA) were performed.

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Drugs stability, concentration of released and loaded drugs were evaluated using HPLC.

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Adhesion of S. aureus clinical and reference strains confirmed the antibaterial properties.

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Performed hybrid layers were cytocompatible (MG-63 tests).

Rapid-Release Griffithsin Fibers for Dual Prevention of HSV-2 and HIV-1 Infections

The biologic griffithsin (GRFT) has recently emerged as a candidate to safely prevent sexually transmitted infections (STIs), including human immunodeficiency virus type 1 (HIV-1) and herpes simplex virus 2 (HSV-2). However, to date, there are few delivery platforms that are available to effectively deliver biologics to the female reproductive tract (FRT). The goal of this work was to evaluate rapid-release polyethylene oxide (PEO), polyvinyl alcohol (PVA), and polyvinylpyrrolidone (PVP) fibers that incorporate GRFT in in vitro (HIV-1 and HSV-2) and in vivo (HSV-2) infection models. GRFT loading was determined via enzyme-linked immunosorbent assay (ELISA), and the bioactivity of GRFT fibers was assessed using in vitro HIV-1 pseudovirus and HSV-2 plaque assays. Afterwards, the efficacy of GRFT fibers was assessed in a murine model of lethal HSV-2 infection. Finally, murine reproductive tracts and vaginal lavage samples were evaluated for histology and cytokine expression, 24 and 72 h after fiber administration, to determine safety. All rapid-release formulations achieved high levels of GRFT incorporation and were completely efficacious against in vitro HIV-1 and HSV-2 infections. Importantly, all rapid-release GRFT fibers provided potent protection in a murine model of HSV-2 infection. Moreover, histology and cytokine levels, evaluated from collected murine reproductive tissues and vaginal lavage samples treated with blank fibers, showed no increased cytokine production or histological aberrations, demonstrating the preliminary safety of rapid-release GRFT fibers in vaginal tissue.

Physico-chemical and biological evaluation of doxycycline loaded into hybrid oxide-polymer layer on Ti-Mo alloy

Oxide-polymer coatings were formed on the surface of the vanadium-free Ti–15Mo titanium alloy. The Ti alloy surface was modified by the plasma electrolytic oxidation process, and then, the polymer layer of a poly (D, l-lactide-co-glycolide) with doxycycline was formed. The polymer evenly covered the porous oxide layer and filled some of the pores. However, the microstructure of the polymer surface was completely different from that of the PEO layer. The surface morphology, roughness and microstructure of the polymer layer were examined by scanning electron microscopy (SEM) and a confocal microscope. The results confirmed the effectiveness of polymer and doxycycline deposition in their stable chemical forms. The drug analysis was performed by high-performance liquid chromatography. The ¹H NMR technique was used to monitor the course of hydrolytic degradation of PLGA. It was shown that the PLGA layer is hydrolysed within a few weeks, and the polyglycolidyl part of the copolymer is hydrolysed to glycolic acid as first and much faster than the polylactide one to lactic acid. This paper presents influence of different microstructures on the biological properties of modified titanium alloys. Cytocompatibility and bacterial adhesion tests were evaluated using osteoblast-like MG-63 cells and using the reference S. aureus and S. epidermidis strains. The results showed that the optimum concentration of doxycycline was found to inhibit the growth of the bacteria and that the layer is still cytocompatible.

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Formation of the oxide-polymer layer containing doxycycline is presented.

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Changes in the doxycycline structure and the evaluation of their stability was analyzed using the HPLC.

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Thickness of the polymer layer was determined using the confocal microscopy.

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The coatings showed the antibacterial properties and were cytocompatible with osteoblast-ike MG-63 cells.

Artificial small-diameter blood vessels: materials, fabrication, surface modification, mechanical properties, and bioactive functionalities

Cardiovascular diseases, especially ones involving narrowed or blocked blood vessels with diameters smaller than 6 millimeters, are the leading cause of death globally. Vascular grafts have been used in bypass surgery to replace damaged native blood vessels for treating severe cardio- and peripheral vascular diseases. However, autologous replacement grafts are not often available due to prior harvesting or the patient's health. Furthermore, autologous harvesting causes secondary injury to the patient at the harvest site. Therefore, artificial blood vessels have been widely investigated in the last several decades. In this review, the progress and potential outlook of small-diameter blood vessels (SDBVs) engineered in vitro are highlighted and summarized, including material selection and development, fabrication techniques, surface modification, mechanical properties, and bioactive functionalities. Several kinds of natural and synthetic polymers for artificial SDBVs are presented here. Commonly used fabrication techniques, such as extrusion and expansion, electrospinning, thermally induced phase separation (TIPS), braiding, 3D printing, hydrogel tubing, gas foaming, and a combination of these methods, are analyzed and compared. Different surface modification methods, such as physical immobilization, surface adsorption, plasma treatment, and chemical immobilization, are investigated and are compared here as well. Mechanical requirements of SDBVs are also reviewed for long-term service. In vitro biological functions of artificial blood vessels, including oxygen consumption, nitric oxide (NO) production, shear stress response, leukocyte adhesion, and anticoagulation, are also discussed. Finally, we draw conclusions regarding current challenges and attempts to identify future directions for the optimal combination of materials, fabrication methods, surface modifications, and biofunctionalities. We hope that this review can assist with the design, fabrication, and application of SDBVs engineered in vitro and promote future advancements in this emerging research field.

In vitro cell delivery by gelatin microspheres prepared in water-in-oil emulsion

The regeneration of injured or damaged tissues by cell delivery approaches requires the fabrication of cell carriers (e.g., microspheres, MS) that allow for cell delivery to limit cells spreading from the injection site. Ideal MS for cell delivery should allow for cells adhesion and proliferation on the MS before the injection, while they should allow for viable cells release after the injection to promote the damaged tissue regeneration. We optimized a water-in-oil emulsion method to obtain gelatin MS crosslinked by methylenebisacrylamide (MBA). The method we propose allowed obtaining spherical, chemically crosslinked MS characterized by a percentage crosslinking degree of 74.5 ± 2.1%. The chemically crosslinked gelatin MS are characterized by a diameter of 70.9 ± 17.2 μm in the dry state and, at swelling plateau in culture medium at 37 °C, by a diameter of 169.3 ± 41.3 μm. The MS show dimensional stability up to 28 days, after which they undergo complete degradation. Moreover, during their degradation, MS release gelatin that can improve the engraftment of cells in the injured site. The produced MS did not induce any cytotoxic effect in vitro and they supported viable L929 fibroblasts adhesion and proliferation. The MS released viable cells able to colonize and proliferate on the tissue culture plastic, used as release substrate, potentially proving their ability in supporting a simplified in vitro wound healing process, thus representing an optimal tool for cell delivery applications.

Advancements and Frontiers in the High Performance of Natural Hydrogels for Cartilage Tissue Engineering

Cartilage injury originating from trauma or osteoarthritis is a common joint disease that can bring about an increasing social and economic burden in modern society. On account of its avascular, neural, and lymphatic characteristics, the poor migration ability of chondrocytes, and a low number of progenitor cells, the self-healing ability of cartilage defects has been significantly limited. Natural hydrogels, occurring abundantly with characteristics such as high water absorption, biodegradation, adjustable porosity, and biocompatibility like that of the natural extracellular matrix (ECM), have been developed into one of the most suitable scaffold biomaterials for the regeneration of cartilage in material science and tissue engineering. Notably, natural hydrogels derived from sources such as animal or human cadaver tissues possess the bionic mechanical behaviors of physiological cartilage that are required for usage as articular cartilage substitutes, by which the enhanced chondrogenic phenotype ability may be achieved by facilely embedding living cells, controlling degradation profiles, and releasing stimulatory growth factors. Hence, we summarize an overview of strategies and developments of the various kinds and functions of natural hydrogels for cartilage tissue engineering in this review. The main concepts and recent essential research found that great challenges like vascularity, clinically relevant size, and mechanical performances were still difficult to overcome because the current limitations of technologies need to be severely addressed in practical settings, particularly in unpredictable preclinical trials and during future forays into cartilage regeneration using natural hydrogel scaffolds with high mechanical properties. Therefore, the grand aim of this current review is to underpin the importance of preparation, modification, and application for the high performance of natural hydrogels for cartilage tissue engineering, which has been achieved by presenting a promising avenue in various fields and postulating real-world respective potentials.

Silk fibroin for skin injury repair: Where do things stand?

Several synthetic and natural materials are used in soft tissue engineering and regenerative medicine with varying degrees of success. Among them, silkworm silk protein fibroin, a naturally occurring protein-based biomaterial, exhibits many promising characteristics such as biocompatibility, controllable biodegradability, tunable mechanical properties, aqueous preparation, minimal inflammation in host tissue, low cost and ease of use. Silk fibroin is often used alone or in combination with other materials in various formats and is also a promising delivery system for bioactive compounds as part of such repair scenarios. These properties make silk fibroin an excellent biomaterial for skin tissue engineering and repair applications. This review focuses on the promising characteristics and recent advances in the use of silk fibroin for skin wound healing and/or soft-tissue repair applications. The benefits and limitations of silk fibroin as a scaffolding biomaterial in this context are also discussed. STATEMENT OF SIGNIFICANCE: Silk protein fibroin is a natural biomaterial with important biological and mechanical properties for soft tissue engineering applications. Silk fibroin is obtained from silkworms and can be purified using alkali or enzyme based degumming (removal of glue protein sericin) procedures. Fibroin is used alone or in combination with other materials in different scaffold forms, such as nanofibrous mats, hydrogels, sponges or films tailored for specific applications. The investigations carried out using silk fibroin or its blends in skin tissue engineering have increased dramatically in recent years due to the advantages of this unique biomaterial. This review focuses on the promising characteristics of silk fibroin for skin wound healing and/or soft-tissue repair applications.

A waterborne polyurethane 3D scaffold containing PLGA with a controllable degradation rate and an anti-inflammatory effect for potential applications in neural tissue repair

3D connected porous LGPU scaffolds with adjustable degradation and a strong anti-inflammatory effect were prepared for neural tissue repair.

Atomic Layer Deposition Coating of TiO2 Nano-Thin Films on Magnesium-Zinc Alloys to Enhance Cytocompatibility for Bioresorbable Vascular Stents

Background and purpose

A coronary stent is a well-known cardiovascular medical device implanted to resolve disorders of the circulatory system due to bloodstream narrowing. Since the implanted device interacts with surrounding biological environments, the surface properties of a typical implantable stent play a critical role in its success or failure. Endothelial cell adhesion and proliferation are fundamental criteria needed for the success of a medical device. Metallic coronary stents are commonly used as biomaterial platforms in cardiovascular implants. As a new generation of coronary stents, bioresorbable vascular scaffolds have attracted a great deal of attention among researchers and studies on bioresorbable materials (such as magnesium and zinc) remain a target for further optimization. However, additional surface modification is needed to control the biodegradation of the implant material while promoting biological reactions without the use of drug elution.

Methods

Herein, precise temperature and thickness controlled atomic layer deposition (ALD) was utilized to provide a unique and conformal nanoscale TiO₂ coating on a customized magnesium-zinc stent alloy.

Results

Impressively, results indicated that this TiO₂ nano-thin film coating stimulated coronary arterial endothelial cell adhesion and proliferation with additional features acting as a protective barrier. Data revealed that both surface morphology and surface hydrophilicity contributed to the success of the ALD nanoscale coating, which further acted as a protection layer inhibiting the release of harmful degradation products from the magnesium-zinc stent.

Conclusion

Overall, the outcome of this in vitro study provided a promising ALD stent coating with unique nano-structural surface properties for increased endothelialization, and as a result, ALD should be further studied for numerous biomedical applications.

Electrospun acid-neutralizing fibers for the amelioration of inflammatory response

Biodegradable aliphatic polyesters, especially polylactide (PLA), polyglycolide (PGA), and their copolymer poly(lactide-co-glycolide) (PLGA), are the most representative and widely used synthetic polymers in the field of tissue engineering and regenerative medicine. However, these polyesters often give rise to aseptic inflammation because of their acidic degradation products after implantation. Here, unidirectional shell-core structured fibers of chitosan/poly(lactide-co-glycolide) (i.e., CTS/PLGA) with acid-neutralizing capability were developed for addressing the noted issue by coating the PLGA fiber surfaces with a layer of the alkaline chitosan by coaxial electrospinning. Our results showed that during a period of 8-week degradation, the shell-layer of chitosan with its unique alkaline nature for acid-neutralization obviously hindered the pH decrease as a result of the degradation of PLGA-core. In a mocked acidic environment testing of the human dermal fibroblasts, chitosan-enabled acidity neutralization could significantly reduce in vitro the secretion of inflammatory factors and downregulate the expression of related inflammatory genes. Thereafter, biocompatibility assessment in vitro showed that the CTS/PLGA fibers had poorer cell adhesion capacity than the PLGA fibers but were cytocompatible and promoted cell migration and secretion of collagen. Moreover, subcutaneous embedding for two and four weeks in vivo revealed that the CTS/PLGA fibers significantly reduced the recruitment of inflammatory cells and the formation of foreign body giant cells (FBGCs). This study thereby demonstrated the evident acid-neutralizing effect of the chitosan-coating layer on alleviating the inflammatory responses caused by the acidic degradation products of the PLGA-core. Our highly aligned CTS/PLGA fibers, as a kind of quasi "pH-neutral fibers" with the acid-neutralizing capability, could be potentially applied for engineering those architecturally anisotropic tissues (e.g., tendon/ligament) toward improved efficacy of regeneration. STATEMENT OF SIGNIFICANCE: It is well known that acidic degradation products from representative aliphatic polyesters (e.g., PLA, PGA, and PLGA) give rise to the problem of aseptic inflammation. Various alkaline components acting as neutralizing agents have been used to address the noted issue. However, rather less attention has been paid to engineer these polyesters into a fibrous form with acid-neutralizing functionality. The present study proposes the concept of "pH-neutral fibers" and develops shell-core structured unidirectional fibers of chitosan/poly(lactide-co-glycolide) with acid-neutralizing capability for ameliorating inflammatory responses caused by the acidic degradation products of PLGA. It provides a comprehensive study encompassing fiber characterization and in vitro and in vivo evaluation, which would pave the way for developing sophisticated pH-neutral fibers for functional tissue regeneration.

Scaffolding Strategies for Tissue Engineering and Regenerative Medicine Applications

During the past two decades, tissue engineering and the regenerative medicine field have invested in the regeneration and reconstruction of pathologically altered tissues, such as cartilage, bone, skin, heart valves, nerves and tendons, and many others. The 3D structured scaffolds and hydrogels alone or combined with bioactive molecules or genes and cells are able to guide the development of functional engineered tissues, and provide mechanical support during in vivo implantation. Naturally derived and synthetic polymers, bioresorbable inorganic materials, and respective hybrids, and decellularized tissue have been considered as scaffolding biomaterials, owing to their boosted structural, mechanical, and biological properties. A diversity of biomaterials, current treatment strategies, and emergent technologies used for 3D scaffolds and hydrogel processing, and the tissue-specific considerations for scaffolding for Tissue engineering (TE) purposes are herein highlighted and discussed in depth. The newest procedures focusing on the 3D behavior and multi-cellular interactions of native tissues for further use for in vitro model processing are also outlined. Completed and ongoing preclinical research trials for TE applications using scaffolds and hydrogels, challenges, and future prospects of research in the regenerative medicine field are also presented.

Biocompatibility and biodegradation properties of polycaprolactone/polydioxanone composite scaffolds prepared by blend or co-electrospinning

Electrospun polymer scaffolds are regarded as an ideal tissue engineering scaffold due to similar morphological properties with the native extracellular matrix. Among these, polycaprolactone is widely used to fabricate electrospun fibrous scaffolds due to its excellent biocompatibility, good mechanical properties, and ease of manufacture. However, its low biodegradation rate has a negative influence on its application in tissue engineering scaffold. To address this issue, this study prepared hybrid scaffolds composed of polycaprolactone and polydioxanone (a fast-degrading polyether-ester) via either the blend or co-electrospinning. Subsequently, the structural characteristics, mechanical strength, in vitro/vivo degradation, cellularization, and vascularization of two kinds of hybrid scaffolds were evaluated to decide which method is more suitable for producing tissue engineering scaffolds. The incorporation of polydioxanone increased the mechanical strength of both composite scaffolds. Moreover, co-electrospun scaffolds exhibited improved hydrophilicity compared to blend scaffolds. The results of in vitro and in vivo degradation studies showed that the degradation rate of both composite scaffolds was faster than that of neat polycaprolactone scaffolds due to the incorporated polydioxanone component. Especially in co-electrospun scaffolds, the fast degradation of polydioxanone fiber gave rise to larger pore size, thus leading to faster cellularization and better vascularization compared to blend scaffolds. Therefore, co-electrospinning was demonstrated to be superior to blend electrospinning for the preparation of composite scaffolds. Co-electrospun polycaprolactone–polydioxanone scaffolds may be promising candidates for tissue engineering.

Pulp-dentin regeneration: current approaches and challenges

Regenerative endodontic procedures for immature permanent teeth with apical periodontitis confer biological advantages such as tooth homeostasis, enhanced immune defense system, and a functional pulp-dentin complex, in addition to clinical advantages such as the facilitation of root development. Currently, this procedure is recognized as a paradigm shift from restoration using materials to regenerate pulp-dentin tissues. Many studies have been conducted with regard to stem/progenitor cells, scaffolds, and biomolecules, associated with pulp tissue engineering. However, preclinical and clinical studies have evidently revealed several drawbacks in the current clinical approach to revascularization that may lead to unfavorable outcomes. Therefore, our review examines the challenges encountered under clinical conditions and summarizes current research findings in an attempt to provide direction for transition from basic research to clinical practice.