A new strategy to characterize the extent of reaction of thermoset elastomers

Exploring the application of poly(1,2-ethanediol citrate)/polylactide nonwovens in cell culturing

Biomaterials containing citric acid as a building unit show potential for use as blood vessel and skin tissue substitutes. The success in commercializing implants containing a polymer matrix of poly(1,8-octanediol citrate) provides a rationale for exploring polycitrates based on other diols. Changing the aliphatic chain length of the diol allows functional design strategies to control the implant's mechanical properties, degradation profile and surface energy. In the present work, poly(1,2-ethanediol citrate) was synthesized and used as an additive to polylactide in the electrospinning process. It was established that the content of polycitrate greatly influences the nonwovens' properties: an equal mass ratio of polymers resulted in the best morphology. The obtained nonwovens were characterized by surface hydrophilicity, tensile strength, and thermal properties. L929 cell cultures were carried out on their surface. The materials were found to be non-cytotoxic and the degree of porosity was suitable for cell colonization. On the basis of the most important parameters for assessing the condition of cultured cells (cell density and viability, cell metabolic activity and lactate dehydrogenase activity), the potential of PLLA + PECit nonwovens for application in tissue engineering was established.

Poly(dimethylsiloxane) as a room-temperature solid solvent for photophysics and photochemistry

Medium viscosity strongly affects the dynamics of solvated species and can drastically alter the deactivation pathways of their excited states. This study demonstrates the utility of poly(dimethylsiloxane) (PDMS) as a room-temperature solid-state medium for optical spectroscopy. As a thermoset elastic polymer, PDMS is transparent in the near ultraviolet, visible, and near infrared spectral regions. It is easy to mould into any shape, forming surfaces with a pronounced smoothness. While PDMS is broadly used for the fabrication of microfluidic devices, it swells in organic solvents, presenting severe limitations for the utility of such devices for applications employing non-aqueous fluids. Nevertheless, this swelling is reversible, which proves immensely beneficial for loading samples into the PDMS solid matrix. Transferring molecular-rotor dyes (used for staining prokaryotic cells and amyloid proteins) from non-viscous solvents into PDMS induces orders-of-magnitude enhancement of their fluorescence quantum yield and excited-state lifetimes, providing mechanistic insights about their deactivation pathways. These findings demonstrate the unexplored potential of PDMS as a solid solvent for optical applications.

Citrate chemistry and biology for biomaterials design

Leveraging the multifunctional nature of citrate in chemistry and inspired by its important role in biological tissues, a class of highly versatile and functional citrate-based materials (CBBs) has been developed via facile and cost-effective polycondensation. CBBs exhibiting tunable mechanical properties and degradation rates, together with excellent biocompatibility and processability, have been successfully applied in vitro and in vivo for applications ranging from soft to hard tissue regeneration, as well as for nanomedicine designs. We summarize in the review, chemistry considerations for CBBs design to tune polymer properties and to introduce functionality with a focus on the most recent advances, biological functions of citrate in native tissues with the new notion of degradation products as cell modulator highlighted, and the applications of CBBs in wound healing, nanomedicine, orthopedic, cardiovascular, nerve and bladder tissue engineering. Given the expansive evidence for citrate's potential in biology and biomaterial science outlined in this review, it is expected that citrate based materials will continue to play an important role in regenerative engineering.

Citrate-Based Biomaterials and Their Applications in Regenerative Engineering

Advances in biomaterials science and engineering are crucial to translating regenerative engineering, an emerging field that aims to recreate complex tissues, into clinical practice. In this regard, citrate-based biomaterials have become an important tool owing to their versatile material and biological characteristics including unique antioxidant, antimicrobial, adhesive, and fluorescent properties. This review discusses fundamental design considerations, strategies to incorporate unique functionality, and examples of how citrate-based biomaterials can be an enabling technology for regenerative engineering.

Regulating the mechanical properties of poly(1,8-octanediol citrate) bioelastomer via loading of chitin nanocrystals

Chitin nanocrystals successfully regulate the modulus and strength of poly(1,8-octanediol citrate) bioelastomer without the sacrifice of elongation.

Deep eutectic solvent-assisted synthesis of biodegradable polyesters with antibacterial properties

Bacterial infection related to the implantation of medical devices represents a serious clinical complication, with dramatic consequences for many patients. In past decades, numerous attempts have been made to develop materials with antibacterial and/or antifouling properties by the incorporation of antibiotic and/or antiseptic compounds. In this context, deep eutectic solvents (DESs) are acquiring increasing interest not only as efficient carriers of active principle ingredients (APIs) but also as assistant platforms for the synthesis of a wide repertoire of polymer-related materials. Herein, we have successfully prepared biodegradable poly(octanediol-co-citrate) polyesters with acquired antibacterial properties by the DES-assisted incorporation of quaternary ammonium or phosphonium salts into the polymer network. In the resulting polymers, the presence of these salts (i.e., choline chloride, tetraethylammonium bromide, hexadecyltrimethylammonium bromide, and methyltriphenylphosphonium bromide) inhibits bacterial growth in the early postimplantation steps, as tested in cultures of Escherichia coli on solid agar plates. Later, positive polymer cytocompatibility is expected to support cell colonization, as anticipated from in vitro preliminary studies with L929 fibroblasts. Finally, the attractive elastic properties of these polyesters permit matching those of soft tissues such as skin. For all of these reasons, we envisage the utility of some of these antibacterial, biocompatible, and biodegradable polyesters as potential candidates for the preparation of antimicrobial wound dressings. These results further emphasize the enormous versatility of DES-assisted synthesis for the incorporation, in the synthesis step, of a wide palette of APIs into polymeric networks suitable for biomedical applications.

Low-pressure foaming: a novel method for the fabrication of porous scaffolds for tissue engineering

Scaffolds for tissue engineering applications must incorporate porosity for optimal cell seeding, tissue ingrowth, and vascularization, but common fabrication methods for achieving porosity are incompatible with a variety of polymers, limiting widespread use. In this study, porous scaffolds consisting of poly(1,8-octanediol-co-citrate) (POC) containing hydroxyapatite nanocrystals (HA) were fabricated using low-pressure foaming (LPF). LPF is a novel method of fabricating an interconnected, porous scaffold with relative ease. LPF takes advantage of air bubbles that act as pore nucleation sites during a polymer mixing step. Vacuum is applied to expand the nucleation sites into interconnected pores that are stabilized through cross-linking. POC was combined with 20%, 40%, and 60% by weight HA, and the effect of increasing HA particle content on porosity, mechanical properties, and alkaline phosphatase (ALP) activity of human mesenchymal stem cells (hMSC) was evaluated. The effect of the prepolymer viscosity on porosity and the mechanical properties of POC with 40% by weight HA (POC-40HA) were also assessed. POC-40HA scaffolds were also implanted in an osteochondral defect of a rabbit model, and the explants were assessed at 6 weeks using histology. With increasing HA content, the pore size of POC-HA scaffolds can be varied (85 to 1,003 μm) and controlled to mimic the pore size of native trabecular bone. The compression modulus increased with greater HA content under dry conditions and were retained to a greater extent than with porous scaffolds fabricated using salt-leaching under wet conditions. Furthermore, all POC-HA scaffolds prepared using LPF supported hMSC attachment, and an increase in ALP activity correlated with an increase in HA content. An increase in the prepolymer viscosity resulted in increased compression modulus, greater distance between pores, and less porosity. After 6 weeks in vivo, cell and tissue infiltration was present throughout the scaffold. This study describes a novel method of creating porous osteoconductive POC scaffolds without the need for porogen leaching and provides the groundwork for applying LPF to other elastomers and composites.