Freeze-casting enables the fabrication of porous scaffolds for bone reconstruction, but the homogeneous dispersion of bioactive glass (BG) in polymer solutions remains challenging. Here, we report, for the first time, the synthesis of core-shell microparticles combining Cu-doped BG with poly(D,L-lactide) (PDLLA) grafted via a surface-initiated "grafting from" approach. Covalent grafting was confirmed by FT-IR spectroscopy and TGA analyses, with grafted chain lengths close to theoretical values. In simulated body fluid (SBF), the PDLLA corona temporarily delayed glass degradation and ion release, mitigating the initial "burst effect", particularly for Cu2+. In vitro, all samples displayed dose-dependent antibacterial and cytotoxic responses, but PDLLA-grafted particles improved cell viability while preserving antibacterial activity. Notably, PDLLA-BG5 achieved the best balance between bacterial inhibition and cytocompatibility. These polymer-grafted, Cu-doped BG microspheres represent promising candidates as building blocks for future PDLLA-based scaffold fabrication via freeze-casting approaches, with scalable processing and tuneable ion-release-driven biological responses.

Polysaccharide-based hydrogels often lack mechanical strength and, when used for protein delivery, are generally limited to diffusion-based release. In this work, we developed robust polysaccharide- and polyester-based near-infrared (NIR)-responsive hydrogels. Hydrogels are made from photo-crosslinked methacrylated dextran (DEX-MA), methacrylated polylactide containing oxygen reactive species (ROS) sensitive thioketal groups (PLA-TK-MA), and covalently bound protoporphyrin IX (PPIX) that generates ROS under NIR irradiation. We investigated the effects of DEX methacrylation degree (3, 12 and 45 %), PLA molecular weight (2500 vs. 5000 g.mol-1) and DEX/PLA ratios (95/5 to 50/50) on the gels' rheological properties. We then examined the NIR-sensitivity of selected hydrogels by comparing their water uptakes and storage/loss moduli. Finally, we studied the release of a model protein, bovine serum albumin (BSA), from the hydrogels with and without NIR-irradiation. Results confirmed that protein release kinetics can be controlled by NIR-irradiation, with faster and complete release of BSA compared to non-irradiated samples.

To develop an orthopedic scaffold that could overcome the limitations of implants used in clinics, we designed poly(ester-urethane) foams and compared their properties with those of a commercial gold standard. A degradable poly(ester-urethane) was synthetized by polyaddition between a diisocyanate poly(ε-caprolactone) prepolymer (PCL di-NCO, Mn = 2400 g·mol−1) and poly(lactic-co-glycolic acid) diol (PLGA, Mn = 2200 g·mol−1) acting as a chain extender. The resulting high-molecular-weight poly(ester-urethane) (PEU, Mn = 87,000 g·mol−1) was obtained and thoroughly characterized by NMR, FTIR and SEC-MALS. The porous scaffolds were then processed using the solvent casting (SC)/particle leaching (PL) method with different NaCl crystal concentrations. The morphology, pore size and porosity of the foams were evaluated using SEM, showing interconnected pores with a uniform size of around 150 µm. The mechanical properties of the scaffolds are close to those of the human meniscus (Ey = 0.5~1 MPa). Their degradation under accelerated conditions confirms that incorporating PLGA into the scaffolds greatly accelerates their degradation rate compared to the gold-standard implant. Finally, a cytotoxicity study confirmed the absence of the cytotoxicity of the PEU, with a 90% viability of the L929 cells. These results suggest that degradable porous PLGA/PCL poly(ester-urethane) has potential in the development of meniscal implants.

Collagen gels are the standard dermal equivalents par excellence, however the problem of rapid cell-mediated contraction remains unresolved. Therefore, the development of hybrid constructs (HCs) based on collagen and polymeric scaffolds is proposed to address the mechanical instability that usually limits the formation of new, functional tissue. Equally important, these synthetic structures should be temporary (degradable) while ensuring that cells are well-adapted to the new extracellular environment. In this study, we screened a library of scaffolds made of various polymers, including homopolymers of polycaprolactone (PCL) and poly D,L-lactide (PLA50), their blends (PCL/PLA50), and copolymers (poly(D,L-lactide-co-caprolactone), PCLLA50) to prepare HCs in a layer-by-layer fashion. The properties of polymers and copolymers along with their processability by electrospinning and 3D-printing were evaluated. Then, we assessed the HCs resistance toward cell-mediated contraction as well as the degradation of the polymeric scaffolds. Our results indicate that scaffolds with higher PLA50 content (e.g., PLA50 100%, PCL/PLA50 or PCLLA50, both at 50/50 caprolactone-to-D,L-lactide molar ratio) presented more drawbacks in terms of handleability and processing, while those with greater PCL presence showed structural steadiness and ease to use. All the scaffolds integrated well with the collagen gel to form the corresponding HCs. With few exceptions, the HCs demonstrated good resistance to cell-derived contraction over 3 weeks. Notably, HCs based on PCLLA50 90/10 (both versions, electrospun or 3D-printed) performed best, showing only a 5%-17% area reduction compared to the 93% observed in collagen-only gels. This copolymer displayed hydrolytic degradation depending on its shape, with up to 45% and 65% loss of molecular weight for the electrospun and 3D-printed forms, respectively, correlating with their progressive change in mechanical features. HCs containing PCLLA50 90/10 also exhibited a better fibroblast distribution, enhanced myofibroblastic differentiation, and a three-fold increase in cell proliferation (when the electrospun type was used) compared to collagen controls. These findings were instrumental in selecting a potential HC that might be used for future experiments in vivo.

The meniscus regeneration can present major challenges such as mimicking tissue microstructuration or triggering cell regeneration. In the case of lesions that require a personalized approach, photoprinting offers the possibility of designing resolutive biomaterial structures. The photo-cross-linkable ink composition determines the process ease and the final network properties. In this study, we designed a range of hybrid inks composed of gelatin(G) and 6-PLA arms(P) that were photo-cross-linked using tyramine groups. The photo-cross-linking efficiency, mechanical properties, degradation, and biological interactions of inks with different G/P mass ratios were studied. The G50P50 network properties were suitable for meniscus regeneration, with Young's modulus of 6.5 MPa, degradation in 2 months, and good cell proliferation. We then confirmed the potential of these inks to produce high-resolution microstructures by printing well-defined microstructures using two-photon polymerization. These hybrid inks offer new perspectives for biocompatible, degradable, and microstructured tissue engineering scaffold creation.

Focusing on the regeneration of damaged knee meniscus, we propose a hybrid scaffold made of poly(ester-urethane) (PEU) and collagen that combines suitable mechanical properties with enhanced biological integration. To ensure biocompatibility and degradability, the degradable PEU was prepared from a poly(epsilon-caprolactone), l-lysine diisocyanate prepolymer (PCL di-NCO) and poly(lactic-co-glycolic acid) diol (PLGA). The resulting PEU (Mn = 52 000 g mol-1) was used to prepare porous scaffolds using the solvent casting (SC)/particle leaching (PL) method at an optimized salt/PEU weight ratio of 5 : 1. The morphology, pore size and porosity of the scaffolds were evaluated by SEM showing interconnected pores with a uniform size of around 170 mu m. Mechanical properties were found to be close to those of the human meniscus (Ey similar to 0.6 MPa at 37 degrees C). To enhance the biological properties, incorporation of collagen type 1 (Col) was then performed via soaking, injection or forced infiltration. The latter yielded the best results as shown by SEM-EDX and X-ray tomography analyses that confirmed the morphology and highlighted the efficient pore Col-coating with an average of 0.3 wt% Col in the scaffolds. Finally, in vitro L929 cell assays confirmed higher cell proliferation and an improved cellular affinity towards the proposed scaffolds compared to culture plates and a gold standard commercial meniscal implant. Focusing on the regeneration of damaged knee meniscus, we propose a hybrid scaffold made of poly(ester-urethane) (PEU) and collagen that combines suitable mechanical properties with enhanced biocompatibility.

In the biomedical field, degradable chemically crosslinked elastomers are interesting materials for tissue engineering applications, since they present rubber-like mechanical properties matching those of soft tissues and are able to preserve their three-dimensional (3D) structure over degradation. Their use in biomedical applications requires surgical handling and implantation that can be a source of accidental damages responsible for the loss of properties. Therefore, their inability to be healed after damage or breaking can be a major drawback. In this work, biodegradable dual-crosslinked networks that exhibit fast and efficient self-healing properties at 37 °C are designed. Self-healable dual-crosslinked (chemically and physically) elastomeric networks are prepared by two methods. The first approach is based on the mix of hydrophobic poly(ethylene glycol)-poly(lactic acid) (PEG-PLA) star-shaped copolymers functionalized with either catechol or methacrylate moieties. In the second approach, hydrophobic bifunctional PEG-PLA star-shaped copolymers with both catechol and methacrylate on their structure are used. In the two systems, the supramolecular network is responsible for the self-healing properties, thanks to the dynamic dissociation/reassociation of the numerous hydrogen bonds between the catechol groups, whereas the covalent network ensures mechanical properties similar to pure methacrylate networks. The self-healable materials display mechanical properties that are compatible with soft tissues and exhibit linear degradation because of the chemical cross-links. The performances of networks from mixed copolymers versus bifunctional copolymers are compared and demonstrate the superiority of the latter. The biocompatibility of the materials is also demonstrated, confirming the potential of these degradable and self-healable elastomeric networks to be used for the design of temporary medical devices.

The design of a biomimetic scaffold is a major challenge in tissue engineering to promote tissue reconstruction. The use of synthetic polymer nanofibers is widely described as they provide biocompatible matrices whose topography mimics natural extracellular matrix (ECM). To closely match the biochemical composition of the ECM, bioactive molecules such as gelatin are added to the nanofibers to enhance cell adhesion and proliferation. To overcome the rapid solubilization of gelatin in biological fluids and to allow a lasting biological effect, the covalent crosslinking of this macromolecule in the network is crucial. The sol-gel route offers the possibility of gentle crosslinking during shaping but is rarely combined with electrospinning. In this study, we present the creation of Poly(lactic acid)/Gelatin hybrid nanofibers by sol-gel route during electrospinning. To enable sol-gel crosslinking, we synthesized star-shaped PLA and functionalized it with silane groups; then we functionalized gelatin with the same groups for their subsequent reaction with the polymer and thus the creation of the hybrid nanonetwork. We evaluated the impact of the presence of gelatin in Poly(lactic acid)/Gelatin hybrid nanofibers at different percentages on the mechanical properties, nanonetwork crosslinking, degradation and biological properties of the hybrid nanofibers. The addition of gelatin modulated nanonetwork crosslinking that impacted the stiffness of the nanofibers, resulting in softer materials for the cells. Moreover, these hybrid nanofibers also showed a significant improvement in fibroblast proliferation and present a degradation rate suitable for tissue reconstruction. Finally, the bioactive hybrid nanofibers possess versatile properties, interesting for various potential applications in tissue reconstruction.

Porous chitosan materials as potential wound dressings were prepared via dissolution of chitosan, nonsolvent-induced phase separation in NaOH-water, formation of a hydrogel, and either freeze-drying or supercritical CO2 drying, leading to "cryogels" and "aerogels", respectively. The hydrophilic drug dexamethasone sodium phosphate was loaded by impregnation of chitosan hydrogel, and the release from cryogel or aerogel was monitored at two pH values relevant for wound healing. The goal was to compare the drug-loading efficiency and release behavior from aerogels and cryogels as a function of the drying method, the materials' physicochemical properties (density, morphology), and the pH of the release medium. Cryogels exhibited a higher loading efficiency and a faster release in comparison with aerogels. A higher sample density and lower pH value of the release medium resulted in a more sustained release in the case of aerogels. In contrast, for cryogels, the density and pH of the release medium did not noticeably influence release kinetics. The Korsmeyer-Peppas model showed the best fit to describe the release from the porous chitosan materials into the different media.

A relevant alternative to enamel matrix derivatives from animal origin could be the use of synthetic amelogenin-derived peptides. This study aimed to assess the effect of a synthetic amelogenin-derived peptide (ADP-5), alone or included in an experimental gellan–xanthan hydrogel, on periodontal cell behavior (gingival fibroblasts, periodontal ligament cells, osteoblasts and cementoblasts). The effect of ADP-5 (50, 100, and 200 µg/mL) on cell metabolic activity was examined using Alamar blue assay, and cell morphology was assessed by confocal imaging. An experimental gellan–xanthan hydrogel was then designed as carrier for ADP-5 and compared to the commercial gel Emdogain®. Alizarin Red was used to determine the periodontal ligament and cementoblasts cell mineralization. The inflammatory profile of these two cells was also quantified using ELISA (vascular endothelial growth factor A, tumor necrosis factor α, and interleukin 11) mediators. ADP-5 enhanced cell proliferation and remineralization; the 100 µg/mL concentration was more efficient than 50 and 200 µg/mL. The ADP-5 experimental hydrogel exhibited equivalent good biological behavior compared to Emdogain® in terms of cell colonization, mineralization, and inflammatory profile. These findings revealed relevant insights regarding the ADP-5 biological behavior. From a clinical perspective, these outcomes could instigate the development of novel functionalized scaffold for periodontal regeneration.

Peritendinous adhesions are complications known to occur up to 6 weeks after surgery and cause chronic pain and disability. Anti-adhesion barriers are currently the best option for prevention. In a previous study, we designed two biodegradable membranes, D-PACO1 and D-PACO(2), based on new triblock copolymers and conducted in vitro evaluations. The membranes maintained filmogenic integrity, had degradation rates that promoted anti-adhesion and were biocompatible, suggesting their safe and effective use as anti-adhesion devices. To test this hypothesis, we conducted a preliminary in vivo study in a rat model of peritendinous adhesions and evaluated the membranes' degradation rates, tendon healing and anti-adhesion effect compared to non-surgical and surgical control groups 2 and 10 weeks after surgery. Macroscopic evaluation showed membranes were effective in reducing the extent and severity of adhesions. Membranes acted as physical barriers at 2 weeks and underwent a complete or significant biodegradation at 10 weeks. D-PACO(2) had a longer degradation rate compared to D-PACO1, was more effective in reducing adhesions and is expected to be more effective in promoting tendon healing. The tendency of D-PACO1 to promote tendon healing while D-PACO(2) did not interfere with healing highlights the need to redesign the porosity of the D-PACO membranes for optimal nutrient diffusion, while maintaining their anti-adhesion effect and clinical usability. Preliminary findings revealed that adhesions form beyond the 6 weeks cited in the literature. In this study, adhesion formation continued for up to 10 weeks, underlining the need to increase the experimental period and sample size of future experiments evaluating anti-adhesion membranes.

PLA nanofibers are of great interest in tissue engineering due to their biocompatibility and morphology; moreover, their physical properties can be tailored for long-lasting applications. One of the common and efficient methods to improve polymer properties and slow down their degradation is sol-gel covalent crosslinking. However, this method usually results in the formation of gels or films, which undervalues the advantages of nanofibers. Here, we describe a dual process sol-gel/electrospinning to improve the mechanical properties and stabilize the degradation of PLA scaffolds. For this purpose, we synthesized star-shaped PLAs and functionalized them with triethoxysilylpropyl groups (StarPLA-PTES) to covalently react during nanofibers formation. To achieve this, we evaluated the use of (1) a polymer diluent and (2) different molecular weights of StarPLA on electrospinnability, StarPLA-PTES condensation time and crosslinking efficiency. Our results show that the diluent allowed the fiber formation and reduced the condensation time, while the addition of low-molecular-weight StarPLA-PTES improved the crosslinking degree, resulting in stable matrices even after 6 months of degradation. Additionally, these materials showed biocompatibility and allowed the proliferation of fibroblasts. Overall, these results open the door to the fabrication of scaffolds with enhanced stability and prospective long-term applications.

Cardiovascular diseases are the leading cause of death globally. Myocardial infarction in particular leads to a high rate of mortality, and in the case of survival, to a loss of myocardial functionality due to post-infarction necrosis. This functionality can be restored by cell therapy or biomaterial implantation, and the need for a rapid regeneration has led to the development of bioactive patches, in particular through the incorporation of growth factors (GF). In this work, we designed hybrid patches composed of polymer nanofibers loaded with HGF and IGF and associated with a collagen membrane. Among the different copolymers studied, the polymers and their porogens PLA-Pluronic-PLA + PEG and PCL + Pluronic were selected to encapsulate HGF and IGF. While 89 and 92% of IGF were released in 2 days, HGF was released up to 58% and 50% in 35 days from PLA-Pluronic-PLA + PEG and PCL + Pluronic nanofibers, respectively. We also compared two ways of association for the loaded nanofibers and the collagen membrane, namely a direct deposition of the nanofibers on a moisturized collagen membrane (wet association), or entrapment between collagen layers (sandwich association). The interfacial cohesion and the degradation properties of the patches were evaluated. We also show that the sandwich association decreases the burst release of HGF while increasing the release efficiency. Finally, we show that the patches are cytocompatible and that the presence of collagen and IGF promotes the proliferation of C2C12 myoblast cells for 11 days. Taken together, these results show that these hybrid patches are of interest for cardiac muscle regeneration.

Tissue adhesives are interesting materials for wound treatment as they present numerous advantages compared to traditional methods of wound closure such as suturing and stapling. Nowadays, fibrin and cyanoacrylate glues are the most widespread commercial biomedical adhesives, but these systems display some drawbacks. In this study, degradable bioadhesives based on PEG-PLA star-shaped hydrogels are designed. Acrylate, methacrylate, and catechol functional copolymers are synthesized and used to design various bioadhesive hydrogels. Various types of mechanisms responsible for adhesion are investigated (physical entanglement and interlocking, physical interactions, chemical bonds), and the adhesive properties of the different systems are first studied on a gelatin model and compared to fibrin and cyanoacrylate references. Hydrogels based on acrylate and methacrylate reached adhesion strength close to cyanoacrylate (332 kPa) with values of 343 and 293 kPa, respectively, whereas catechol systems displayed higher values (11 and 19 kPa) compared to fibrin glue (7 kPa). Bioadhesives were then tested on mouse skin and human cadaveric colonic tissue. The results on mouse skin confirmed the potential of acrylate and methacrylate gels with adhesion strength close to commercial glues (15-30 kPa), whereas none of the systems led to high levels of adhesion on the colon. These data confirm that we designed a family of degradable bioadhesives with adhesion strength in the range of commercial glues. The low level of cytotoxicity of these materials is also demonstrated and confirm the potential of these hydrogels to be used as surgical adhesives.

Electrospun scaffolds combine suitable structural characteristics that make them strong candidates for their use in tissue engineering. These features can be tailored to optimize other physiologically relevant attributes (e.g. mechanical anisotropy and cellular affinity) while ensuring adequate degradation rates of the biomaterial. Here, we present the fabrication of microstructured scaffolds by using a combination of micropatterned electrospinning collectors (honeycomb- or square-patterned) and poly(lactic acid) (PLA)-based copolymers (linear or star-shaped). The resulting materials showed appropriate macropore size and fiber alignment that were key parameters to enhance their anisotropic properties in protraction. Moreover, their elastic modulus, which was initially similar to that of soft tissues, gradually changed in hydrolytic conditions, matching the degradation profile in a 2- to 3-month period. Finally, honeycomb-structured scaffolds exhibited enhanced cellular proliferation compared to standard electrospun mats, while cell colonization was shown to be guided by the macropore contour. Taking together, these results provide new insight into the rational design of microstructured materials that can mimic the progressive evolution of properties in soft tissue regeneration.

There is a growing interest in magnetic nanocomposites in biomaterials science. In particular, nanocomposites that combine poly(lactide) (PLA) nanofibers and superparamagnetic iron oxide nanoparticles (SPIONs), which can be obtained by either electrospinning of a SPION suspension in PLA or by precipitating SPIONs at the surface of PLA, are well documented in the literature. However, these two classical processes yield nanocomposites with altered materials properties, and their long-term in vivo fate and performances have in most cases only been evaluated over short periods of time. Recently, we reported a new strategy to prepare well-defined PLA@SPION nanofibers with a quasi-monolayer of SPIONs anchored at the surface of PLA electrospun fibers. Herein, we report on a 6-month in vivo rat implantation study with the aim of evaluating the long-term magnetic resonance imaging (MRI) properties of this new class of magnetic nanocomposites, as well as their tissue integration and degradation. Using clinically relevant T2-weighted MRI conditions, we show that the PLA@SPION nanocomposites are clearly visible up to 6 months. We also evaluate here by histological analyses the slow degradation of the PLA@SPIONs, as well as their biocompatibility. Overall, these results make these nanocomposites attractive for the development of magnetic biomaterials for biomedical applications.

Polymer vectors for gene therapy have been largely investigated as an alternative to viral vectors. In particular, double hydrophilic block copolymers (DHBCs) have shown potential in this domain, but to date studies mainly focus on non-degradable copolymers, which may be a restriction for further development. To overcome this limitation, we synthesized a DHBC (PEG(43)-b-PCL12 (COOH)(6.5)) composed of a polyethylene glycol) (PEG) non-ionic and bioeliminable block and a degradable carboxylic acid-functionalized poly(epsilon-caprolactone) (PCL) block. The potential of this DHBC as an original vector for small interfering ribonucleic acids (siRNA) to formulate tripartite polyionic complex (PIC) micelles with poly(lysine) (PLL) was evaluated. We first studied the impact of the charge ratio (R) on the size and the zeta potential of the resulting micelles. With a charge ratio R = 1, one formulation with optimized physico-chemical properties showed the ability to complex 75% of siRNA. We showed a stability of the micelles at pH 7.4 and a disruption at pH 5, which allowed a pH-triggered siRNA release and proved the pH-stimuli responsive character of the tripartite micelles. In addition, the tripartite PIC micelles were shown to be non-cytotoxic below 40 mu g/mL. The potential of these siRNA vectors was further evaluated in vitro: it was found that the tripartite PIC micelles allowed siRNA internalization to be 3 times higher than PLL polyplexes in murine mesenchymal stem cells, and were able to transfect human breast cancer cells. Overall, this set of data pre-validates the use of degradable DHBC as non-viral vectors for the encapsulation and the controlled release of siRNA, which may therefore constitute a sound alternative to nondegradable and/or cytotoxic polycationic vectors. (C) 2020 Elsevier Inc. All rights reserved.

New synthetic textiles with physical and/or biological properties are increasingly used in medical applications [1,2]. While a simple textile coating is usually carried out to obtain biological properties, covalent grafting should be considered for long-term applications. Herein, we have developed a new hybrid bioactive nylon whose synthesis involves a peptide sequence with a diacyl derivative. Numerous types of peptide-nylons were prepared by varying the molar percentage (0.1%, 1% and 10%) and orientation of the peptide in the polymer backbone. Nylons incorporating antibacterial peptides significantly inhibited S. aureus proliferation whereas nylons functionalized with cell-adhesive peptide enhanced the proliferation of L929 fibroblast. These results show that the incorporation of the peptides directly into the nylon skeleton is efficient and provides biological properties that suggest new ways of functionalizing biomedical textiles.