Controlled release of bioactive IL-2 from visible light photocured biodegradable elastomers for cancer immunotherapy applications

Biodegradable elastomeric controlled-release poly (decane-co-tricarballylate) (PDET) based matrices capable of maintaining the stability and bioactivity of Interleukin-2 (IL-2) through the utilization of visible-light curing and solvent-free loading of the cytokine are reported. The elastomeric devices were fabricated by intimately mixing lyophilized IL-2 powder with the acrylated prepolymer before photocrosslinking. The bioactivity of the released protein was assessed by its ability to stimulate the proliferation of the C57BL/6 mouse cytotoxic T lymphocyte, and its concentration was analysed using ELISA. The influence of changes in the polymer's physicochemical and mechanical properties on IL-2 release kinetics and bioactivity were also studied. The increase in the device's surface area and the incorporation of trehalose in the loaded lyophilized mix increased the IL-2 release rate with drug release proceeding via typical zero-order release kinetics. Moreover, the decrease in the degree of acrylation of the prepared devices increased the IL-2 release rate. The bioactivity assay showed that IL-2 retained over 94% of its initial bioactivity throughout 28 days of the release period. A new protein delivery vehicle composed of biodegradable PDET elastomers was demonstrated to be promising and effective for linear, constant, and sustained osmotic-driven release of bioactive IL-2 and other sensitive proteins and hormones.

Synthesis, characterization & cytocompatibility of poly (diol-co-tricarballylate) based thermally crosslinked elastomers for drug delivery & tissue engineering applications

The aim of this study was to investigate the synthesis and in vitro characterization of thermoset biodegradable poly (diol-co-tricarballylate) (PDT) elastomeric polymers for the purpose of their use in implantable drug delivery and tissue engineering applications. The synthesis was based on thermal crosslinking technique via a polycondensation reaction of tricarballylic acid with aliphatic diols of varying chain lengths (C6-C12). PDT prepolymers were synthesized at 140 °C for 20 min. After purification, the prepolymers were molded and kept at 120 °C for 18 h under vacuum to complete the crosslinking process. PDT prepolymers were characterized by DSC, FT-IR, ¹H NMR and GPC. The PDT elastomers were also subjected to thermal and structural analysis, as well as sol content, mechanical testing, in vitro degradation and cytocompatibility studies. The mechanical properties and sol content were found to be dependent on synthesis conditions and can be controlled by manipulating the crosslinking density and number of methylene groups in the chain of precursor aliphatic diol. The family of thermally crosslinked PDT biodegradable polyesters were successfully prepared and characterized; besides they have promising use in drug delivery and other biomedical tissue engineering applications.

New Three-Dimensional Poly(decanediol-co-tricarballylate) Elastomeric Fibrous Mesh Fabricated by Photoreactive Electrospinning for Cardiac Tissue Engineering Applications

Reactive electrospinning is capable of efficiently producing in situ crosslinked scaffolds resembling the natural extracellular matrix with tunable characteristics. In this study, we aimed to synthesize, characterize, and investigate the in vitro cytocompatibility of electrospun fibers of acrylated poly(1,10-decanediol-co-tricarballylate) copolymer prepared utilizing the photoreactive electrospinning process with ultraviolet radiation for crosslinking, to be used for cardiac tissue engineering applications. Chemical, thermal, and morphological characterization confirmed the successful synthesis of the polymer used for production of the electrospun fibrous scaffolds with more than 70% porosity. Mechanical testing confirmed the elastomeric nature of the fibers required to withstand cardiac contraction and relaxation. The cell viability assay showed no significant cytotoxicity of the fibers on cultured cardiomyoblasts and the cell-scaffolds interaction study showed a significant increase in cell attachment and growth on the electrospun fibers compared to the reference. This data suggests that the newly synthesized fibrous scaffold constitutes a promising candidate for cardiac tissue engineering applications.

Biodegradable star-shaped polycyclic ester elastomers: Preparation, degradability, protein release, and biocompatibility in vitro

Effective local delivery methods for sustained and stable release of protein drugs are urgently needed. Biodegradable elastomers based on star-shaped polycyclic esters have received attention for their drug-loading and drug-release kinetics. However, the long degradation periods resulting from their strong lipophilicity greatly hinder their application. In this study, we synthesized new cross-linked elastomers based on methyl-acrylic-star-poly(ϵ-caprolactone- co-d,l-lactide) cyclic ester and methyl-bi-acrylic-poly(ϵ-caprolactone-b-poly(ethylene glycol)-b-ϵ-caprolactone) with different molecular weights; determined their physical, thermal, and morphological characteristics; and studied their in vitro degradation and release of bovine serum albumin and recombinant human interleukin 2. Elastomer hydrophilicity improved with the introduction of methyl-bi-acrylic-poly(ϵ-caprolactone-b-poly(ethylene glycol)-b-ϵ-caprolactone), and a shorter degradation period (~25 weeks) was achieved. Additionally, the degradation rate could be adjusted by varying the composition of methyl-bi-acrylic-poly(ϵ-caprolactone-b-poly(ethylene glycol)-b-ϵ-caprolactone) to directly influence the degree of swelling, cross-linking density, and sol content of the elastomer. The controlled rate of bovine serum albumin and recombinant human interleukin 2 release increased with a larger degree of swelling, higher sol content, and lower cross-link density of the elastomers. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide analysis showed good biocompatibility. These results suggest that these new elastomers are potential candidates for carrier materials in controlled, implantable delivery systems for protein drugs and other biomedical applications.

Photo-irradiation paradigm: Mapping a remarkable facile technique used for advanced drug, gene and cell delivery

Undoubtedly, the progression of photo-irradiation technique has provided a smart engineering tool for the state-of-the-art biomaterials that guide the biomedical and therapeutic domains for promoting the modern pharmaceutical industry. Many investigators had exploited such a potential technique to create/ameliorate numerous pharmaceutical carriers. These carriers show promising applications that vary from small drug to therapeutic protein delivery and from gene to living cell encapsulation design. Harmony between the properties of precisely engineered precursors and the formed network structure broadens the investigator's intellect for both brilliant creations and effective applications. As well, controlling photo-curing at the formulation level, through manipulating the absorption of light stimuli, photoinitiator system and photo-responsive precursor, facilitates the exploration of novel distinctive biomaterials. Discussion of utilizing different photo-curing procedures in designing/formulation of different pharmaceutical carriers is the main emphasis of this review. In addition, recent applications of these intelligent techniques in targeted, controlled, and sustained drug delivery with understanding of photo-irradiation concept and mechanism are illustrated.

Biocompatibility and biodegradability of implantable drug delivery matrices based on novel poly(decane-co-tricarballylate) photocured elastomers

Visible light photo-cross-linked biodegradable amorphous elastomers based on poly(decane- co-tricarballylate) (PDET) with different cross-linking densities were synthesized, and their cytotoxicity, biocompatibility, and biodegradability were reported. Cytotoxicity of PDET extracts of the elastomers was assessed for mitochondrial succinate dehydrogenase activity by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT assay) and inhibition of [3H] thymidine incorporation into DNA of epithelial cells. The in vivo biocompatibility and biodegradability were determined by subcutaneous implantation of PDET microcylinders in 25 male Sprague–Dawley rats over a period of 12 weeks. The in vivo changes in physical and mechanical parameters of the implants were compared with those observed in vitro. The treated epithelial cells revealed no signs of cytotoxicity, and the elastomer degradation products caused only a slight stimulation to both mitochondrial activity and DNA replication. The implants did not exhibit any macroscopic signs of inflammation or adverse tissue reactions at implant retrieval sites. The retrieved implanted microcylinders maintained their original geometry and extensibility in a manner similar to those observed in vitro. These new elastomers have excellent biocompatibility and are considered promising biomaterials for controlled drug delivery and tissue engineering applications.