Copolymerization of Natural Camphor-Derived Rigid Diol with Various Dicarboxylic Acids: Access to Biobased Polyesters with Various Properties

Melt Polycondensation Strategy for Amide-Functionalized l-Aspartic Acid Amphiphilic Polyester Nano-assemblies and Enzyme-Responsive Drug Delivery in Cancer Cells

Aliphatic polyesters are intrinsically enzymatic-biodegradable, and there is ever-increasing demand for safe and smart next-generation biomaterials including drug delivery nano-vectors in cancer research. Using bioresource-based biodegradable polyesters is one of the elegant strategies to meet this requirement; here, we report an l-amino acid-based amide-functionalized polyester platform and explore their lysosomal enzymatic biodegradation aspects to administrate anticancer drugs in cancer cells. l-Aspartic acid was chosen and different amide-side chain-functionalized di-ester monomers were tailor-made having aromatic, aliphatic, and bio-source pendant units. Under solvent-free melt polycondensation methodology; these monomers underwent polymerization to yield high molecular weight polyesters with tunable thermal properties. PEGylated l-aspartic monomer was designed to make thermo-responsive amphiphilic polyesters. This amphiphilic polyester was self-assembled into a 140 ± 10 nm-sized spherical nanoparticle in aqueous medium, which exhibited lower critical solution temperature at 40-42 °C. The polyester nano-assemblies showed excellent encapsulation capabilities for anticancer drug doxorubicin (DOX), anti-inflammatory drug curcumin, biomarkers such as rose bengal (RB), and 8-hydroxypyrene-1,3,6-trisulfonic acid trisodium salt. The amphiphilic polyester NP was found to be very stable under extracellular conditions and underwent degradation upon exposure to horse liver esterase enzyme in phosphate-buffered saline at 37 °C to release 90% of the loaded cargoes. Cytotoxicity studies in breast cancer MCF 7 and wild-type mouse embryonic fibroblasts cell lines revealed that the amphiphilic polyester was non-toxic to cell lines up to 100 μg/mL, while their drug-loaded polyester nanoparticles were able to inhibit the cancerous cell growth. Temperature-dependent cellular uptake studies further confirmed the energy-dependent endocytosis of polymer NPs across the cellular membranes. Confocal laser scanning microscopy assisted time-dependent cellular uptake analysis directly evident for the endocytosis of DOX loaded polymer NP and their internalization for biodegradation. In a nutshell, the present investigation opens up an avenue for the l-amino acid-based biodegradable polyesters from l-aspartic acids, and the proof of concept is demonstrated for drug delivery in the cancer cell line.

New Random Aromatic/Aliphatic Copolymers of 2,5-Furandicarboxylic and Camphoric Acids with Tunable Mechanical Properties and Exceptional Gas Barrier Capability for Sustainable Mono-Layered Food Packaging

High molecular weight, fully biobased random copolymers of 2,5-furandicarboxylic acid (2,5-FDCA) containing different amounts of (1R, 3S)-(+)-Camphoric Acid (CA) have been successfully synthesized by two-stage melt polycondensation and compression molding in the form of films. The synthesized copolyesters have been first subjected to molecular characterization by nuclear magnetic resonance spectroscopy and gel-permeation chromatography. Afterward, the samples have been characterized from a thermal and structural point of view by means of differential scanning calorimetry, thermogravimetric analysis, and wide-angle X-ray scattering, respectively. Mechanical and barrier properties to oxygen and carbon dioxide were also tested. The results obtained revealed that chemical modification permitted a modulation of the abovementioned properties depending on the amount of camphoric co-units present in the copolymers. The outstanding functional properties promoted by camphor moieties addition could be associated with improved interchain interactions (π-π ring stacking and hydrogen bonds).

Bio-Degradable Polyesters with Rigid Cyclic Diester from Camphor and Tartaric Acid

Despite their excellent, useful, and stable properties, thermoplastics are constantly subject to environmental risks because of their low degradability under thermal, chemical, and mechanical stresses. To overcome the aforementioned issues, we hereby introduce an eco-friendly camphor (Ct) cyclic diester. The Ct diester is designed as a monomer, including a ketal group from the Ct, and shows high thermal stability via a rigid spiro-ring and a bridged bicyclic structure. A series of polyester was synthesized using the Ct diester, including various types of diols and dimethyl terephthalate. PETxCty copolyesters showed appropriate thermal stability up to 414 °C and a high glass transition temperature. This thermal behavior led to amorphous regions as the Ct diester content increased. Regarding the proportion of the Ct diester in the polyester, it was sensitive to hydrolysis and contributed to the degradation of the polyester in acid buffer conditions.

Recent Progress on Bio-Based Polyesters Derived from 2,5-Furandicarbonxylic Acid (FDCA)

The big challenge today is the upgrading of sustainable materials to replace miscellaneous ones from petroleum resources. Thus, a generic bio-based building block lays the foundation of the huge bio-market to green economy. 2,5-Furandicarboxylic acid (FDCA), a rigid diacid derived from lignocellulose or fructose, represents a great potential as a contender to terephthalic acid (TPA). Recently, studies on the synthesis, modification, and functionalization of bio-based polyesters based on FDCA have attracted widespread attention. To apply furanic polyesters on engineering plastics, packaging materials, electronics, etc., researchers have extended the properties of basic FDCA-based homo-polyesters by directional copolymerization and composite preparation. This review covers the synthesis and performance of polyesters and composites based on FDCA with emphasis bedded on the thermomechanical, crystallization, barrier properties, and biodegradability. Finally, a summary of what has been achieved and the issues waiting to be addressed of FDCA-based polyester materials are suggested.

Chemical Modification of Poly(butylene trans-1,4-cyclohexanedicarboxylate) by Camphor: A New Example of Bio-Based Polyesters for Sustainable Food Packaging

Among the several actions contributing to the development of a sustainable society, there is the eco-design of new plastic materials with zero environmental impact but that are possibly characterized by properties comparable to those of the traditional fossil-based plastics. This action is particularly urgent for food packaging sector, which involves large volumes of plastic products that quickly become waste. This work aims to contribute to the achievement of this important goal, proposing new bio-based cycloaliphatic polymers based on trans-1,4-cyclohexanedicarboxylic acid and containing different amount of camphoric acid (from 0 to 15 mol %), a cheap and bio-based building block. Such chemical modification was conducted in the melt by avoiding the use of solvents. The so-obtained polymers were processed in the form of films by compression molding. Afterwards, the new and successfully synthesized random copolymers were characterized by molecular (NMR spectroscopy and GPC analysis), thermal (DSC and TGA analyses), diffractometric (wide angle X-ray scattering), mechanical (through tensile tests), and O2 and CO2 barrier point of view together with the parent homopolymer. The article aims to relate the results obtained with the amount of camphoric moiety introduced and to present, the different microstructure in the copolymers in more detail; indeed, in these samples, a different crystalline form developed (the so-called β-PBCE). This latter form was the kinetically favored and less packed one, as proven by the lower equilibrium melting temperature determined for the first time by Baur's equation.