Photochemical reactivity of PLA at the vicinity of glass transition temperature. The photo-rheology method

Vegetal Polyphenol Extracts as Antioxidants for the Stabilization of PLA: Toward Fully Biobased Polymer Formulation

The use of natural antioxidants as substitutes for traditional synthetic stabilizers has been investigated for the stabilization of biobased and biodegradable polymers, with the aim of designing fully biobased plastic formulations. This study focused on the thermo- and photostabilization of poly(lactic acid) (PLA) using vegetal polyphenol extracts as biosourced antioxidants. The polyphenols were extracted by microwave-assisted extraction from the valorization of vegetal waste, and their potential as antioxidant additives was evaluated (e.g., polyphenol content, composition, and antioxidant activity). PLA was then formulated with 2 wt % of the extracts exhibiting the highest antioxidant activities: green tea residues, pomegranate peels, grape marc, bramble leaves, and yellow onion peel extracts. The efficiency of the natural additives as thermal stabilizers was evaluated and compared with a synthetic antioxidant using rheological and thermal analyses. The results demonstrated the capacity of grape marc extract and pomegranate peel extract to significantly improve PLA thermal stability during processing and thermo-oxidation. Finally, photorheology was conducted to evaluate the influence of the bioadditives on the biopolyester photodegradation. The different polyphenol extracts seemed to significantly hinder the photo-oxidation of PLA and constitute very promising natural UV stabilizers, combining UV absorbers and antioxidant functions.

Development of a microfluidic photochemical flow reactor concept by rapid prototyping

The transfer from batch to flow chemistry is often based on commercial microfluidic equipment, such as costly complete reactor systems, which cannot be easily tailored to specific requirements of technologies such as DNA-encoded library technology (DELT), in particular for increasingly important photochemical reactions. Customized photoreactor concepts using rapid prototyping technology offer a modular, flexible, and affordable design that allows for adaptation to various applications. In order to validate the prototype reactors, a photochemical pinacol coupling reaction at 368 nm was conducted to demonstrate the transfer from batch to flow chemistry. The conversion rates were optimized by adapting the design parameters of the microfluidic flow photoreactor module. Subsequently, the photoreactor module has been extended to an application with DNA-tagged substrates by switching to LEDs with a wavelength of 454 nm. The successful recovery of DNA confirmed the feasibility of the modular-designed flow photo reactor. This collaborative approach holds enormous potential to drive the development of DELT and flow equipment design.

The role of waste management in reducing bioplastics' leakage into the environment: A review

Bioplastics are becoming more and more widespread as substitutes for petroleum-derived plastics due to their biodegradability. Bioplastics degradation under different environments has been described and reported to depend mainly on bioplastics' compositions and the environmental conditions. Incomplete degradation during waste management processes and leakage of bioplastics into the environment are becoming major concerns that need to be further investigated. In this context, the present paper aimed to review recent literature dealing with biodegradation of bioplastics under industrial (e.g. anaerobic digestion and composting) and natural (e.g. soil and water) environments, and to link it to the potential bioplastics' leakage into the environment. Reviewed data were used to estimate the potential role of waste management processes in decreasing the potential leakage of bioplastics. Depending on bioplastics' type and processing conditions, waste management can effectively reduce bioplastics' potential leakage, decreasing the concentration of these materials that can reach the natural environments.

Degradation of bioplastics in organic waste by mesophilic anaerobic digestion, composting and soil incubation

The aim of the study was to assess the effects of high concentrations (10 % w/w, data projected for 2030) of commercial bioplastics, i.e. starch based shopping bags (SBSB) and polylactic acid (PLA) tableware, in the organic fraction of municipal solid wastes (MSW) on compost quality obtained by pilot-scale dry mesophilic anaerobic digestion and subsequent composting of the digestate. After the biological processes, 48.1 % total solids (TS) of SBSB and 15 % TS of PLA degraded, resulting in a high bioplastics content (about 18 % TS) in compost. Subsequent compost incubation in soils indicated that bioplastics degraded by pseudo-zero order kinetics (0.014 and 0.010 mg C cm^-2 d^-1 for SBSB and PLA, respectively), i.e. complete degradation was expected in 1.6 years (SBSB) and 7.2 years (PLA), confirming the intrinsic biodegradability of bioplastics. Nevertheless, enhancing the rate and amount of bioplastics degradation during waste management represents a goal to decrease the amount of bioplastics reaching the environment.

Synthesis of Poly(l-lactide-co-ε-caprolactone) Copolymer: Structure, Toughness, and Elasticity

Biodegradable and bioabsorbable polymers have drawn considerable attention because of their mechanical properties that mimic human soft tissue. Poly(l-lactide-co-ε-caprolactone) (PLCL), the copolymer of L-lactic (LA) and ε-caprolactone (CL), has been applied in many tissue engineering and regenerative medicine fields. However, both the synthesis of PLCL and the structure-activity relationship of the copolymer need to be further investigated to allow tuning of different mechanical properties. The synthesis conditions of PLCL were optimized to increase the yield and improve the copolymer properties. The synthetic process was evaluated by while varying the molar ratio of the monomers and polymerization time. The mechanical properties of the copolymer were investigated from the macroscopic and microscopic perspectives. Changes in the polymerization time and feed ratio resulted in the difference in the LA and CL content, which, in turn, caused the PLCL to exhibit different properties. The PLCL obtained with a feed ratio of 1:1 (LA:CL) and a polymerization time of 30 h has the best toughness and elasticity. The developed PLCL may have applications in dynamic mechanical environment, such as vascular tissue engineering.

Polylactic Acid-Based Patterned Matrixes for Site-Specific Delivery of Neuropeptides On-Demand: Functional NGF Effects on Human Neuronal Cells

The patterned microchamber arrays based on biocompatible polymers are a versatile cargo delivery system for drug storage and site-/time-specific drug release on demand. However, functional evidence of their action on nerve cells, in particular their potential for enabling patterned neuronal morphogenesis, remains unclear. Recently, we have established that the polylactic acid (PLA)-based microchamber arrays are biocompatible with human cells of neuronal phenotype and provide safe loading for hydrophilic substances of low molecular weight, with successive site-specific cargo release on-demand to trigger local cell responses. Here, we load the nerve growth factor (NGF) inside microchambers and grow N2A cells on the surface of patterned microchamber arrays. We find that the neurite outgrowth in local N2A cells can be preferentially directed towards opened microchambers (upon-specific NGF release). These observations suggest the PLA-microchambers can be an efficient drug delivery system for the site-specific delivery of neuropeptides on-demand, potentially suitable for the migratory or axonal guidance of human nerve cells.