Smart Packaging Based on Polylactic Acid: The Effects of Antibacterial and Antioxidant Agents from Natural Extracts on Physical-Mechanical Properties, Colony Reduction, Perishable Food Shelf Life, and Future Prospective

Changes in consumer lifestyles have raised awareness of a variety of food options and packaging technologies. Active and smart packaging is an innovative technology that serves to enhance the safety and quality of food products like fruit, vegetables, fish, and meat. Smart packaging, as a subset of this technology, entails the integration of additives into packaging materials, thereby facilitating the preservation or extension of product quality and shelf life. This technological approach stimulates a heightened demand for safer food products with a prolonged shelf life. Active packaging predominantly relies on the utilization of natural active substances. Therefore, the combination of active substances has a significant impact on the characteristics of active packaging, particularly on polymeric blends like polylactic acid (PLA) as a matrix. Therefore, this review will summarize how the addition of natural active agents influences the performance of smart packaging through systematic analysis, providing new insights into the types of active agents on physical-mechanical properties, colony reduction, and its application in foods. Through their integration, the market for active and smart packaging systems is expected to have a bright future.

Effect of cold plasma treatment on polylactic acid and polylactic acid/poly (ethylene glycol) films developed as a drug delivery system for streptomycin sulfate

Polylactic acid (PLA) being a renewable polyester have extensively researched in the biomedical field due to its non-toxicity, high biocompatibility, and easy processing properties. However, low functionalization ability and hydrophobicity limit its applications and hence demands physical and chemical modifications to overcome these limitations. Cold plasma treatment (CPT) is frequently used to improve the hydrophilic properties of PLA-based biomaterials. This provides an advantage to obtain a controlled drug release profile in drug delivery systems. The rapid drug release profile may be advantageous in some applications such as wound application. The main objective of this study is to determine the effects of CPT on PLA or PLA@polyethylene glycol (PLA@PEG) porous films fabricated by solution casting method for use as a drug delivery system with a rapid release profile. The physical, chemical, morphological and drug release properties of PLA and PLA@PEG films, such as surface topography, thickness, porosity, water contact angle (WCA), chemical structure, and streptomycin sulfate release properties, after CPT were systematically investigated. XRD, XPS and FTIR results showed that oxygen-containing functional groups were formed on the film surface with CPT without changing the bulk properties. Along with the changes in the surface morphology such as surface roughness and porosity, the new functional groups provide the films hydrophilic properties by reducing the water contact angle. The improved surface properties enabled the selected model drug, streptomycin sulfate, to exhibit a faster release profile with drug-released mechanism fitted by first order kinetic model. Considering all the results, the prepared films showed an enormous potential for future drug delivery applications, especially in wound application where rapid drug release profile is an advantage.

Multi-faceted analysis of thermophilic anaerobic biodegradation of poly(lactic acid)-based material

Currently, the production of bio-based polymeric materials, of which poly(lactic acid) (PLA) is the most popular, has been increasing, causing the growth of PLA waste in municipal waste. Thus, it is necessary to develop sustainable methods for treating it. Methane production, resulting from anaerobic digestion (AD), is a potential end-of-life scenario for PLA waste that needs to be investigated. To obtain high efficiency of AD, thermophilic fermentation was applied, and to overcome low rates of biodegradation, hydrothermal (HT) and alkaline (A) pretreatments were used. For a deep insight into the process, differential scanning calorimetry (DSC), Fourier-transform infrared spectroscopy (FTIR), and microscopic and microbial analyses (based on 16S rDNA) were applied. For both untreated (PLA) and pretreated (PLA_HT, PLA_A) samples a high maximal methane production (MP) of 453 L/kg volatile solids (VS) was obtained, almost 100 % of the theoretical methane yield from PLA. The use of pretreatment allowed shortening of the time for obtaining maximal MP, especially the hydrothermal pretreatment, which shortened the overall time of MP 1.3-fold, and methane was produced at an almost 10 % higher rate (8.35 vs 7.79 L/(kg VS·d)). However, DSC and microscopic analyses revealed that, in all cases, methane was intensively produced i) after the reduction of the molecular mass of the PLA material and ii) also when PLA pieces were not visible. This should be considered when designing the operational time for the AD process. Parallel to the gradual biodegradation of PLA, the abundances of Firmicutes, Thermotogae, and Euryarcheota increased. With PLA_HT, Syntrophobacteraceae, Thermoanaerobacteraceae, and methanogens were identified as potential key thermophilic PLA biodegraders.

Photolithographically Patterned Cell-Repellent PEG-b-PTHPMA Diblock Copolymer for Guided Cell Adhesion and Growth

Surfaces for guided cell adhesion and growth are indispensable in several diagnostic and therapeutic applications. Towards this direction, four diblock copolymers comprising polyethylene glycol (PEG) and poly(2-tetrahydropyranyl methacrylate) (PTHPMA) are synthesized employing PEG macroinitiators of different chain lengths. The copolymer with a 5000 Da PEG block and a PEG-PTHPMA comonomers weight ratio of 43-57 provides a film with the highest stability in the culture medium and the strongest cell repellent properties. This copolymer is used to develop a positive photolithographic material and create stripe patterns onto silicon substrates. The highest selectivity regarding smooth muscle cell adhesion and growth and the highest fidelity of adhered cells for up to 3 days in culture is achieved for stripe patterns with widths between 25 and 27.5 µm. Smooth muscle cells cultured on such patterned substrates exhibit a decrease in their proliferation rate and nucleus area and an increase in their major axis length, compared to the cells cultured onto non-patterned substrates. These alterations are indicative of the adoption of a contractile rather than a synthetic phenotype of the smooth muscle cells grown onto the patterned substrates and demonstrate the potential of the novel photolithographic material and patterning method for guided cell adhesion and growth.

Effect of maleic anhydride grafted poly(lactic acid) on rheological behaviors and mechanical performance of poly(lactic acid)/poly(ethylene glycol) (PLA/PEG) blends

A series of polylactic acid (PLA)/polyethylene glycol (PEG) blends was prepared by melt blending using PEG as a plasticizer to address the disadvantages of PLA brittleness. PEG can weaken the intermolecular chain interactions of PLA and improve its processing properties. PLA-grafted maleic anhydride (GPLA) was reactively blended with PLA/PEG to obtain a high tenacity PLA/PEG/GPLA blend. GPLA was prepared by melt grafting using diisopropyl peroxide as the initiator and maleic anhydride as the graft. The effects of different PEG molecular weights (1000–10 000 g mol⁻¹) on the properties of PLA/PEG/GPLA blends were investigated. GPLA reacted with PEG1000 (M_w = 1000 g mol⁻¹) to form short PLA branched chains and reacted with PEG10000 (M_w = 10 000 g mol⁻¹) to form a small number of PLA branched chains, which was unconducive to increasing the intermolecular chain entanglement. The branched PLA formed by the reaction between PEG6000 (M_w = 6000 g mol⁻¹) and GPLA had a remarkable effect on increasing intermolecular chain entanglement. The complex viscosity, modulus, and melt strength values of PLA/PEG6000/GPLA blends were relatively large. The elongation at break of the blends reached 526.9%, and the tensile strength was 30.91 MPa. It provides an effective way to prepare PLA materials with excellent comprehensive properties.

Preparation of PLA/PEG/GPLA blends with high toughness by reactive blending of PLA grafted maleic anhydride (GPLA).