A biodegradable thermoset polymer made by esterification of citric acid and glycerol

Design Strategies and Applications of Biomaterials and Devices for Hernia Repair

Hernia repair is one of the most commonly performed surgical procedures worldwide, with a multi-billion dollar global market. Implant design remains a critical challenge for the successful repair and prevention of recurrent hernias, and despite significant progress, there is no ideal mesh for every surgery. This review summarizes the evolution of prostheses design toward successful hernia repair beginning with a description of the anatomy of the disease and the classifications of hernias. Next, the major milestones in implant design are discussed. Commonly encountered complications and strategies to minimize these adverse effects are described, followed by a thorough description of the implant characteristics necessary for successful repair. Finally, available implants are categorized and their advantages and limitations elucidated, including non-absorbable and absorbable (synthetic and biologically derived) prostheses, composite prostheses, and coated prostheses. This review not only summarizes the state of the art in hernia repair, but also suggests future research directions toward improved hernia repair utilizing novel materials and fabrication methods.

Post polymer modification of polyethylenimine with citrate esters: selectivity and hydrophobicity

Hydrophobic modification of water soluble PEI with citrate esters is selective and increases log P_oct.

Exploiting a new glycerol-based copolymer as a route to wound healing: Synthesis, characterization and biocompatibility assessment

The use of biocompatible materials based on naturally derived monomers plays a key role in pharmaceutical and cosmetic industries. In this paper we describe the synthesis of a new low molecular weight copolymer, based on glycerol and l-tartaric acid, useful to develop biocompatible dermal patches with drug delivery properties. The copolymer's chemical composition was assessed by FT-IR (Fourier transform infrared spectroscopy), (1)H NMR ((1)H Nuclear Magnetic Resonance) and XPS (X-ray photoelectron spectroscopy), while its molecular weight distribution was estimated by SEC (size exclusion chromatography). Copolymer thermal properties were studied by TGA (thermogravimetric analysis). Biological evaluations by MTT assay and SEM (scanning electron microscopy) observations performed with murine fibroblasts and human keratinocytes (HaCaT) revealed a good compatibility of the proposed copolymer. Ciprofloxacin was selected as model drug and its release was evaluated by HPLC (high performance liquid chromatography), showing that the new copolymer supplied promising results as drug delivery system for wound healing applications. Furthermore, investigations on Skin-Mesenchymal stem cells (S-MSCs) behaviour and gene expression showed that the copolymer and its combination with ciprofloxacin did not affect their stemness. In this regard, the fabrication of dermal patches with new, low cost materials for local treatment of skin infections represents an attractive strategy in order to bypass the worrying side effects of systemic antibiotic therapy. Overall, the performed physico-chemical characterization, drug release test and biological evaluations showed that this new copolymer could be a promising tool for the in situ delivery of bioactive molecules during skin lesions treatment.

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.

Prebiotic alternatives to proteins: structure and function of hyperbranched polyesters

Proteins are responsible multiple biological functions, such as ligand binding, catalysis, and ion channeling. This functionality is enabled by proteins' three-dimensional structures that require long polypeptides. Since plausibly prebiotic synthesis of functional polypeptides has proven challenging in the laboratory, we propose that these functions may have been initially performed by alternative macromolecular constructs, namely hyperbranched polymers (HBPs), during early stages of chemical evolution. HBPs can be straightforwardly synthesized in one-pot processes, possess globular structures determined by their architecture as opposed to folding in proteins, and have documented ligand binding and catalytic properties. Our initial study focuses on glycerol-citric acid HBPs synthesized via moderate heating in the dry state. The polymerization products consisted of a mixture of isomeric structures of varying molar mass as evidenced by NMR, mass spectrometry and size-exclusion chromatography. Addition of divalent cations during polymerization resulted in increased incorporation of citric acid into the HBPs and the possible formation of cation-oligomer complexes. The chelating properties of citric acid govern the makeup of the resulting polymer, turning the polymerization system into a rudimentary smart material.

Developing chemoselective and biodegradable polyester elastomers for bioscaffold application

Thermal polyesterification has emerged as a successful method for synthesizing polyesters for biomedical applications. However, to date, no general functionalization strategy has been incorporated into materials designed by the thermal polycondensation of polyacids and polyols. Herein, we report the design of several elastomers based on the thermal polycondensation of 4-ketopimelic acid, citric acid, and one of two diols: 1,6-hexanediol or 1,4-cyclohexanedimethanol. By varying the diol and the curing conditions, several elastomers were designed with a range of physical and mechanical properties. Poly(diol 4-ketopimelate-co-diol citrate) achieved Young's modulus, ultimate tensile stress, and rupture strain values of 0.39-1.13 MPa, 0.27-1.04 MPa, and 108-426%, respectively. Additionally, the incorporation of the ketone from 4-ketopimelic acid gave these materials two advantageous characteristics: a site for covalent functionalization through oxime formation and the ability to covalently bond to the surrounding tissue through imine linkages. Biocompatibility was studied both in vitro and in vivo in order to gain a complete understanding as to how biological systems respond to these novel materials. Based on preliminary results, we believe that poly(diol 4-ketopimelate-co-diol citrate) polyketoesters are excellent candidates for biomaterials.

New biomaterials from renewable resources – amphiphilic block copolymers from δ-decalactone

Polymers for drug delivery applications have been synthesised via environmentally benign routes and with sustainable feedstocks.

Diglycerol-based polyesters: melt polymerization with hydrophobic anhydrides

The melt polymerization of diglycerol with bicyclic anhydride monomers derived from a naturally occurring monoterpene provides an avenue for polyesters with a high degree of sustainability. The hydrophobic anhydrides are synthesized at ambient temperature via a solvent-free Diels-Alder reaction of α-phellandrene with maleic anhydride. Subsequent melt polymerizations with tetra-functional diglycerol are effective under a range of [diglycerol]/[anhydride] ratios. The hydrophobicity of α-phellandrene directly impacts the swelling behavior of the resulting polyesters. The low E factors (<2), large amount of bio-based content (>75%), ambient temperature monomer synthesis, and polymer degradability represent key factors in the design of these sustainable polyesters.