Covalently Bonded N-Acetylcysteine-polyester Loaded in PCL Scaffolds for Enhanced Interactions with Fibroblasts

Collagen-decorated electrospun scaffolds of unsaturated copolyesters for bone tissue regeneration

Many efforts have been devoted to bone tissue to regenerate damaged tissues, and the development of new biocompatible materials that match the biological, mechanical, and chemical features required for this application is crucial. Herein, a collagen-decorated scaffold was prepared via electrospinning using a synthesized unsaturated copolyester (poly(globalide-co-pentadecalactone)), followed by two coupling reactions: thiol-ene functionalization with cysteine and further conjugation via EDC/NHS chemistry with collagen, aiming to design a bone tissue regeneration device with improved hydrophilicity and cell viability. Comonomer ratios were varied, affecting the copolymer's thermal and chemical properties and highlighting the tunable features of this copolyester. Functionalization with cysteine created new carboxyl and amine groups needed for bioconjugation with collagen, which is responsible for providing biological and structural integrity to the extra-cellular matrix. Bioconjugation with collagen turned the scaffold highly hydrophilic, decreasing its contact angle from 107 ± 2° to 0°, decreasing the copolymer crystallinity by 71%, and improving cell viability by 85% compared with the raw scaffold, thus promoting cell growth and proliferation. The highly efficient and biosafe strategy to conjugate polymers and proteins created a promising device for bone repair in tissue engineering.

Characterization of Gelatin-Polycaprolactone Membranes by Electrospinning

New advances in materials science and medicine have enabled the development of new and increasingly sophisticated biomaterials. One of the most widely used biopolymers is polycaprolactone (PCL) because it has properties suitable for biomedical applications, tissue engineering scaffolds, or drug delivery systems. However, PCL scaffolds do not have adequate bioactivity, and therefore, alternatives have been studied, such as mixing PCL with bioactive polymers such as gelatin, to promote cell growth. Thus, this work will deal with the fabrication of nanofiber membranes by means of the electrospinning technique using PCL-based solutions (12 wt.% and 20 wt.%) and PCL with gelatin (12 wt.% and 8 wt.%, respectively). Formic acid and acetic acid, as well as mixtures of both in different proportions, have been used to prepare the preliminary solutions, thus supporting the electrospinning process by controlling the viscosity of the solutions and, therefore, the size and uniformity of the fibers. The physical properties of the solutions and the morphological, mechanical, and thermal properties of the membranes were evaluated. Results demonstrate that it is possible to achieve the determined properties of the samples with an appropriate selection of polymer concentrations as well as solvents.

Nanofiber Scaffolds as Drug Delivery Systems Promoting Wound Healing

Nanofiber scaffolds have emerged as a revolutionary drug delivery platform for promoting wound healing, due to their unique properties, including high surface area, interconnected porosity, excellent breathability, and moisture absorption, as well as their spatial structure which mimics the extracellular matrix. However, the use of nanofibers to achieve controlled drug loading and release still presents many challenges, with ongoing research still exploring how to load drugs onto nanofiber scaffolds without loss of activity and how to control their release in a specific spatiotemporal manner. This comprehensive study systematically reviews the applications and recent advances related to drug-laden nanofiber scaffolds for skin-wound management. First, we introduce commonly used methods for nanofiber preparation, including electrostatic spinning, sol-gel, molecular self-assembly, thermally induced phase separation, and 3D-printing techniques. Next, we summarize the polymers used in the preparation of nanofibers and drug delivery methods utilizing nanofiber scaffolds. We then review the application of drug-loaded nanofiber scaffolds for wound healing, considering the different stages of wound healing in which the drug acts. Finally, we briefly describe stimulus-responsive drug delivery schemes for nanofiber scaffolds, as well as other exciting drug delivery systems.

Coating of SPIONs with a Cysteine-Decorated Copolyester: A Possible Novel Nanoplatform for Enzymatic Release

Superparamagnetic iron oxide nanoparticles (SPIONs) have their use approved for the diagnosis/treatment of malignant tumors and can be metabolized by the organism. To prevent embolism caused by these nanoparticles, they need to be coated with biocompatible and non-cytotoxic materials. Here, we synthesized an unsaturated and biocompatible copolyester, poly (globalide-co-ε-caprolactone) (PGlCL), and modified it with the amino acid cysteine (Cys) via a thiol-ene reaction (PGlCLCys). The Cys-modified copolymer presented reduced crystallinity and increased hydrophilicity in comparison to PGlCL, thus being used for the coating of SPIONS (SPION@PGlCLCys). Additionally, cysteine pendant groups at the particle’s surface allowed the direct conjugation of (bio)molecules that establish specific interactions with tumor cells (MDA-MB 231). The conjugation of either folic acid (FA) or the anti-cancer drug methotrexate (MTX) was carried out directly on the amine groups of cysteine molecules present in the SPION@PGlCLCys surface (SPION@PGlCLCys_FA and SPION@PGlCLCys_MTX) by carbodiimide-mediated coupling, leading to the formation of amide bonds, with conjugation efficiencies of 62% for FA and 60% for MTX. Then, the release of MTX from the nanoparticle surface was evaluated using a protease at 37 °C in phosphate buffer pH~5.3. It was found that 45% of MTX conjugated to the SPIONs were released after 72 h. Cell viability was measured by MTT assay, and after 72 h, 25% reduction in cell viability of tumor cells was observed. Thus, after a successful conjugation and subsequent triggered release of MTX, we understand that SPION@PGlCLCys has a strong potential to be treated as a model nanoplatform for the development of treatments and diagnosis techniques (or theranostic applications) that can be less aggressive to patients.

Synthesis, characterization, thermal stability, and in vitro and in vivo degradation study of polycaprolactone and polyglycolide block copolymers

Biodegradable polymer materials are attractive in various biomedical applications. Herein, we report a block aliphatic copolymer, polycaprolactone-block-polyglycolide (PCL-b-PGA, denoted as PCLGA), and explored the polymer composition effect on the thermal and degradation behaviors. Three copolymers with different PCL/PGA weight ratios were obtained by a two-step ring opening polymerization. The chemical structures and compositions of copolymers were studied by NMR and FT-IR. The thermal behaviors were investigated by DSC and TGA. The in vitro degradation in phosphate buffer saline and in vivo degradation as an implant in rats were evaluated and the hygroscopic rate and polymer weight loss changes were monitored in an eight-week period. PCLGA with a higher PCL composition showed a slower degradation in vitro and in vivo. These PCLGAs with different degradation rates could be used as biomedical implants for potential application in drug delivery and tissue repair.

Electrospun Poly(acrylic acid-co-4-styrene sulfonate) as Potential Drug-Eluting Scaffolds for Targeted Chemotherapeutic Delivery Systems on Gastric (AGS) and Breast (MDA-Mb-231) Cancer Cell Lines

Potential drug-eluting scaffolds of electrospun poly(acrylic acid-co-styrene sulfonate) P(AA-co-SS) in clonogenic assays using tumorigenic gastric and ovarian cancer cells were tested in vitro. Electrospun polymer nanofiber (EPnF) meshes of PAA and PSSNa homo- and P(AA-co-SS) copolymer composed of 30:70, 50:50, 70:30 acrylic acid (AA) and sodium 4-styrene sulfonate (SSNa) units were performed by electrospinning (ES). The synthesis, structural and morphological characterization of all EPnF meshes were analyzed by optical and electron microscopy (SEM-EDS), infrared spectroscopy (FTIR), contact angle, and X-ray diffraction (XRD) measurements. This study shows that different ratio of AA and SSNa of monomers in P(AA-co-SS) EPnF play a crucial role in clonogenic in vitro assays. We found that 50:50 P(AA-co-SS) EPnF mesh loaded with antineoplastic drugs can be an excellent suppressor of growth-independent anchored capacities in vitro assays and a good subcutaneous drug delivery system for chemotherapeutic medication in vivo model for surgical resection procedures in cancer research.

Enzymatic Synthesis of Polyesters and Their Bioapplications: Recent Advances and Perspectives

This article reviews the most important advances in the enzymatic synthesis of polyesters. In first place, the different processes of polyester enzymatic synthesis, i.e., polycondensation, ring opening, and chemoenzymatic polymerizations, and the key parameters affecting these reactions, such as enzyme, concentration, solvent, or temperature, are analyzed. Then, the latest articles on the preparation of polyesters either by direct synthesis or via modification are commented. Finally, the main bioapplications of enzymatically obtained polyesters, i.e., antimicrobial, drug delivery, or tissue engineering, are described. It is intended to point out the great advantages that enzymatic polymerization present to obtain polymers and the disadvantages found to develop applied materials.