Environmental problems, such as global warming and plastic pollution have forced researchers to investigate alternatives for conventional plastics. Poly(lactic acid) (PLA), one of the well-known eco-friendly biodegradables and biobased polyesters, has been studied extensively and is considered to be a promising substitute to petroleum-based polymers. This review gives an inclusive overview of the current research of lactic acid and lactide dimer techniques along with the production of PLA from its monomers. Melt polycondensation as well as ring opening polymerization techniques are discussed, and the effect of various catalysts and polymerization conditions is thoroughly presented. Reaction mechanisms are also reviewed. However, due to the competitive decomposition reactions, in the most cases low or medium molecular weight (MW) of PLA, not exceeding 20,000-50,000 g/mol, are prepared. For this reason, additional procedures such as solid state polycondensation (SSP) and chain extension (CE) reaching MW ranging from 80,000 up to 250,000 g/mol are extensively investigated here. Lastly, numerous practical applications of PLA in various fields of industry, technical challenges and limitations of PLA use as well as its future perspectives are also reported in this review.

Poly(lactic Acid): A Versatile Biobased Polymer for the Future with Multifunctional Properties-From Monomer Synthesis, Polymerization Techniques and Molecular Weight Increase to PLA Applications.

Edible coatings and antimicrobial nanoemulsions for enhancing shelf life and reducing foodborne pathogens of fruits and vegetables: A review

Polymeric microparticles (MPs) are recognized as very popular carriers to increase the bioavailability and bio-distribution of both lipophilic and hydrophilic drugs. Among different kinds of polymers, poly-(lactic-co-glycolic acid) (PLGA) is one of the most accepted materials for this purpose, because of its biodegradability (due to the presence of ester linkages that are degraded by hydrolysis in aqueous environments) and safety (PLGA is a Food and Drug Administration (FDA)-approved compound). Moreover, its biodegradability depends on the number of glycolide units present in the structure, indeed, lower glycol content results in an increased degradation time and conversely a higher monomer unit number results in a decreased time. Due to this feature, it is possible to design and fabricate MPs with a programmable and time-controlled drug release. Many approaches and procedures can be used to prepare MPs. The chosen fabrication methodology influences size, stability, entrapment efficiency, and MPs release kinetics. For example, lipophilic drugs as chemotherapeutic agents (doxorubicin), anti-inflammatory non-steroidal (indomethacin), and nutraceuticals (curcumin) were successfully encapsulated in MPs prepared by single emulsion technique, while water-soluble compounds, such as aptamer, peptides and proteins, involved the use of double emulsion systems to provide a hydrophilic compartment and prevent molecular degradation. The purpose of this review is to provide an overview about the preparation and characterization of drug-loaded PLGA MPs obtained by single, double emulsion and microfluidic techniques, and their current applications in the pharmaceutical industry.Graphic abstract.

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Recent advances in the formulation of PLGA microparticles for controlled drug delivery

Novel biopolymer-based sustainable composites for food packaging applications: A narrative review

Quaternary ammonium salts of chitosan. A critical overview on the synthesis and properties generated by quaternization

Highly efficient antifogging and antibacterial food packaging film fabricated by novel quaternary ammonium chitosan composite.

The objective of this work is to explore a new pathway to develop active packaging materials. Currently, controlled release materials have attracted considerable attention in food packaging applications. In this study, the thyme essential oil (TEO) was loaded in electrospinning porous poly(lactic acid) (PLA) nanofibers and coated with poly(vinyl alcohol)/poly(ethylene glycol) (PVA/PEG) blends for humidity-controlled TEO release. The images of scanning electron microscope displayed uniform pores distributed on the surface of PLA nanofibers. Water contact angle measurement indicated that PVA/PEG coating provided the packaging film with excellent hydrophilicity. ATR-FTIR spectral analysis supported the chemical composition of the films. The antibacterial activities of PLA/TEO/PVA/PEG films against Escherichia coli and Staphylococcus aureus reached ＞99%. Furthermore, the weight loss and firmness of strawberries packaged with this novel film were evaluated. Finally, the in vitro release behaviors of TEO were evaluated and the results demonstrated that the release rate could be controlled by adjusting the humidity (20% RH to 80% RH).

Novel antimicrobial packaging film based on porous poly(lactic acid) nanofiber and polymeric coating for humidity-controlled release of thyme essential oil

Electrospun pullulan/PVA nanofibers integrated with thymol-loaded porphyrin metal-organic framework for antibacterial food packaging.

Multifunctional DNA Hydrogels with Hydrocolloid-Cotton Structure for Regeneration of Diabetic Infectious Wounds

Thymol has been shown to be a safe and effective broad-spectrum antimicrobial agent that can be used as a food preservative. However, its volatile characteristics and strong odor limit its use in food products. The microencapsulation of this essential oil in biopolymers could overcome these disadvantages. In this work, thymol-loaded poly(lactide-co-glycolide) (PLGA) microparticles were successfully prepared and the optimal encapsulation efficiency was obtained at 20% (w/w) thymol. Microparticles containing thymol presented a spherical shape and smooth surface. Microencapsulation significantly improved the thermal and storage stability of thymol. In vitro release profiles demonstrated an initial fast release followed by a slow and sustained release. Thymol-loaded microparticles had strong antibacterial activity against Escherichia coli and Staphylococcus aureus, and the effectiveness of their antibacterial properties was confirmed in a milk test. Therefore, the thymol-loaded microparticles show great potential for use as an antimicrobial and as preservation additives in food.

https://www.mdpi.com/1996-1944/12/7/1133/pdf

Tiantian Min

Papers

Highly efficient antifogging and antibacterial food packaging film fabricated by novel quaternary ammonium chitosan composite.

Novel antimicrobial packaging film based on porous poly(lactic acid) nanofiber and polymeric coating for humidity-controlled release of thyme essential oil

Electrospun pullulan/PVA nanofibers integrated with thymol-loaded porphyrin metal-organic framework for antibacterial food packaging.

Multifunctional DNA Hydrogels with Hydrocolloid-Cotton Structure for Regeneration of Diabetic Infectious Wounds

Microencapsulation of Thymol in Poly(lactide-co-glycolide) (PLGA): Physical and Antibacterial Properties.