Preparation and properties of biodegradable antibacterial polylactic acid/modified chitin antibacterial agent composites

Novel composite 3D-printed filament made from fish scale-derived hydroxyapatite, eggshell and polylactic acid via a fused fabrication approach

Driven by environmental sustainability, research in composite materials has seen a surge in interest in biodegradable materials. There is a growing trend among researchers to utilize biodegradable and renewable materials, which enhances the perception of ecological safety. Even though bio-based materials such as poly (lactic) acid (PLA) are biodegradable and completely recyclable, they come up lacking in satisfying certain material requirements such as high thermal stability, mechanical strength, impact resistance, and environmental resistance. Researchers are exploring natural fibers like kenaf to address this challenge and promote sustainability as reinforcements for PLA composites. Despite this, a significant barrier to completion persists in unsatisfactory mechanical performance due to the poor adhesion at the interface between hydrophilic kenaf and hydrophobic PLA. A potential solution to this challenge could involve the incorporation of nano-clay into the natural fiber composites. The enhanced interfacial interaction between the reinforcing material and poly (lactic) acid (PLA) imparts superior properties to composites when the nano-clay is incorporated. This review article examines how incorporating nanoclay into these composites can bridge this gap by enhancing the interfacial bonding between PLA and natural fiber reinforcement. Furthermore, an assessment is conducted on the mechanical properties of natural fiber composites reinforced with nano-clay and kenaf, polymers, and nano-clay. This research is particularly pertinent to the development of automotive applications.

In order to reduce environmental pollution and resource waste, food packaging materials should not only have good biodegradable ability but also effective antibacterial properties. Poly(lactic acid) (PLA) is the most commonly used biopolymer for food packaging applications. PLA has good physical properties, mechanical properties, biodegradability, and cell compatibility but does not have inherent antibacterial properties. Therefore, antibacterial packaging materials based on PLA need to add antibacterial agents to the polymer matrix. Natural antibacterial agents are widely used in food packaging materials due to their low toxicity. The high volatility of natural antibacterial agents restricts their application in food packaging materials. Therefore, appropriate processing methods are particularly important. This review introduces PLA-based natural antibacterial food packaging, and the composition and application of natural antibacterial agents are discussed. The properties of natural antibacterial agents, the technology of binding with the matrix, and the effect of inhibiting various bacteria are summarized.

The aim of the study was to establish the influence of poly(ethylene glycol) (PEG) on the properties of potential biodegradable packaging materials with antibacterial properties, based on polylactide (PLA) and tea tree essential oil (TTO). The obtained polymeric films consisted of PLA, a natural biocide, and tea tree essential oil (5–20 wt. %) was prepared with or without an addition of 5 wt. % PEG. The PLA-based materials have been tested, taking into account their morphology, and their thermal, mechanical and antibacterial properties against Staphylococcus aureus and Escherichia coli. It was established that the introduction of a plasticizer into the PLA–TTO systems leads to an increase in tensile strength, resistance to deformation, as well an increased thermal stability, in comparison to films modified using only TTO. The incorporation of 5 wt. % PEG in the PLA solution containing 5 wt. % TTO allowed us to obtain a material exhibiting a satisfactory antibacterial effect on both groups of representative bacteria. The presented results indicated a beneficial effect of PEG on the antibacterial and functional properties of materials with the addition of TTO.

Polylactic acid (PLA) is a high-modulus, high-strength bio-based thermoplastic polyester with good biodegradability, which is currently a promising environmentally friendly material. However, its inherent brittleness has hindered its widespread use. In this study, we reported a simple and non-toxic strategy for toughening PLA, using biodegradable materials such as polyethylene glycol (PEG) and citric acid (CA) as precursors. Through reactive melt blending with PLA, PEG and CA form PEGCA copolyesters in situ during blending. At the same time, CA can react with PLA and PEG, forming a copolyester structure at the interface of the two phases, improving the interfacial compatibility between PEG and PEGCA with PLA. Fourier transform infrared spectroscopy confirms this. Experimental results show that when the content of PEG/CA reaches 15% (PLA/PEG/CA-15%) in the blends, the impact strength of the blend was 4.47 kJ m-2, and the maximum elongation at break was as high as 360.1%, which were about 2 and 44 times higher than those of pure PLA, respectively. Moreover, the tensile strength was still maintained at the level of 70%. This work can expand the application of PLA in food packaging and medical supplies.

We herein evaluated the antibacterial effect of curry plant EO, a natural antibacterial agent, on B. cereus. The curry plant EO was encapsulated into liposomes to improve the chemical stability of EO and its active time. By a thin‐film dispersion method, soy lecithin, in combination with cholesterol, were used to prepare liposomes at various curry plant EO concentrations. The optimal formula for preparing liposome is a curry plant EO concentration of 5.0 mg/ml. The average particle size of liposomes containing curry plant EO was 196.6 nm with a PDI of 0.218 and the entrapment efficiency was 56.34%. The optimal liposomes containing curry plant EO gave a zeta potential of −31.1 mV. Besides, liposome‐encapsulated curry plant EO exhibited efficient antimicrobial activity for B. cereus in rice.Practical applicationsAs a natural and safe antibacterial agent, curry plant EO shows an excellent antibacterial effect on B. cereus in rice. The concept in the present study may be useful in the future to deliver a variety of antimicrobials for the treatment of various infections caused by bacteria or other organisms. Hence, the antimicrobial agent has broad prospect in the field of food preservation.

Synergistic effects of TMC series nucleating agent and poly(ethylene glycol) on poly(lactic acid) based films: Mechanical, crystallization, storage, and optical properties.

Polylactic acid (PLA) is a biopolymer that has potentialfor usein food packaging applications; however, its low crystallinity andpoor gas barrier properties limit its use. This study aimed to increasethe understanding of the structure property relation of biopolymerblends and their nanocomposites. The crystallinity of the final materialsand their effect on barrier properties was studied. Two strategieswere performed: first, different concentrations of poly(hydroxybutyrate)(PHB; 10, 25, and 50 wt %) were compounded with PLA to facilitatethe PHB spherulite development, and then, for further increase ofthe overall crystallinity, glycerol triacetate (GTA) functionalizedchitin nanocrystals (ChNCs) were added. The PLA:PHB blend with 25wt % PHB showed the formation of many very small PHB spherulites withthe highest PHB crystallinity among the examined compositions andwas selected as the matrix for the ChNC nanocomposites. Then, ChNCswith different concentrations (0.5, 1, and 2 wt %) were added to the75:25 PLA:PHB blend using the liquid-assisted extrusion process inthe presence of GTA. The addition of the ChNCs resulted in an improvementin the crystallization rate and degree of PHB crystallinity as wellas mechanical properties. The nanocomposite with the highest crystallinityresulted in greatly decreased oxygen (O) and carbondioxide (CO2) permeability and increased the overall mechanicalproperties compared to the blend with GTA. This study shows that theaddition ChNCs in PLA:PHB can be a possible way to reach suitablegas barrier properties for food packaging films.

This work investigates the construction of biodegradable packaging film based on polylactic acid (PLA) reinforced with a novel antibacterial hybrid nanofiller to improve barrier and mechanical properties. The study focuses on incorporating silver‐ingrained silica particles (Ag–In–Si) into PLA matrix to prepare the packaging film (Ag–In–SiPLA) that has superior antibacterial, and barrier property with negligible oxygen and water vapour penetration. The Ag was synthesized using natural neem leaf extract as a reducing agent. To ingrain silver over rice husk silica (Si) an in situ technique was adopted. Hence called Ag‐In‐Si bio‐filler. The Ag–In–SiPLA films were fabricated using melt blending and sheet extrusion methods by means of a micro‐compounder. The addition of rice husk silica served the purpose of cost‐effectiveness of the packaging film along with the enhancement of the oxygen and water barrier properties of the films. The optimized sample (PLA loaded with 3% Ag–In–Si), exhibited optimum transparency, moisture resistance, and barrier properties compared with control PLA film. The experiments on Muntingia calabura (Jamaica cherry) preservation have verified the remarkable effectiveness of Ag–In–SiPLA films in preserving their quality for an extended period. These biodegradable packaging films, composed of food‐grade materials and sustainable ingredients, have the potential to provide a compostable and environmentally friendly solution for various packaging applications. This research shed light on the antibacterial Ag–In–SiPLA film as a long‐term, high‐performance fruit packaging solution.Highlights Novel antibacterial PLA composite with enhanced barrier and mechanical properties. Silver‐ingrained silica particles improve antibacterial and barrier properties. Green synthesis of silver using neem leaf extract Melt blending and sheet extrusion used to create cost‐effective packaging films. Ag–In–SiPLA films extend Muntingia calabura preservation, proving effective.

The CO 2 permeability and mixed gas CO 2/H 2 selectivity of membranes composed of CO 2-philic polymers

A strategy to overcome the brittleness and rigidity of polylactic acid (PLA)-based materials for food packaging applications is adding a proper plasticizer in the right amount. Here, triacetin (TA) and polyethylene glycol (PEG) were used as plasticizers in different amounts (10, 20, and 30 wt%) to produce the plasticized PLA films by the solvent-casting method. Tensile properties, water vapor permeability (WVP), moisture content (MC), optical properties, Fourier transform infrared absorption (FTIR), and thermogravimetric analysis (TGA) are reported. The results showed that both TA and PEG cause increasing elongation at break (Eab) and decreasing tensile strength (TS), where the plasticized PLA films containing 10 and 30 wt% of TA showed the highest TS (26.6 MPa) and Eab (81.1%), respectively. Light transmission of PLA was decreased by introducing the plasticizers, while WVP, MC, and opacity of the plasticized films were increased compared to the neat PLA. Among the plasticized films, the sample with 10 wt% of TA and PEG showed the lowest WVP (4.9 × 10−10 g/m s−1 Pa−1) and MC (5.5%), respectively. Based on the TGA, an improvement in the thermal stability of TA and PEG plasticized films compared to the neat PLA was obvious. The sample containing 10 wt% of TA (PLA-TA10) showed the best performance for food packaging applications. Practical applications Food product packaging provides retarding deterioration, reducing microbial contamination, preserving safety, protecting quality, and extending the shelf life of packaged foods during transmission, storage, and consumption. Petroleum-based plastic and synthetic polymers have been mainly used in food packaging due to their cheap cost and good mechanical and barrier properties. However, increasing the use of these nonbiodegradable polymers causes serious environmental and health problems. The biopolymers which are extracted from biodegradable and renewable sources are considered as suitable alternatives for petroleum-based plastic materials. However, application of biopolymers as packaging materials has been limited due to their low mechanical properties and thermal stability. Many studies have been conducted to modify the properties of PLA-based packaging materials to create a favorable product for the food industry. Moreover, introducing plasticizer to PLA helps to develop biocomposite materials with unique characteristics for food packaging. This article shows an improvement in the properties of the PLA-based composites for food packaging applications.

Electrospinning of gelatin/chitosan nanofibers incorporated with tannic acid and chitooligosaccharides on polylactic acid film: Characteristics and bioactivities

Hybrid nanostructures can be developed with inorganic nanoparticles (NPs) such as zinc oxide (ZnO) and natural antibacterials. ZnO NPs can also exert antibacterial effects, and we used them here to examine their dual action in combination with a natural antibacterial agent, protocatechuic acid (PCA). To produce hybrid nanoformulations, we functionalized ZnO NPs with four types of silane organic molecules and successfully linked them to PCA. Physicochemical assessment confirmed PCA content up to ~18% in hybrid nanoformulations, with a PCA entrapment efficiency of ~72%, indicating successful connection. We then investigated the in vitro release kinetics and antibacterial effects of the hybrid against Staphylococcus aureus. PCA release from hybrid nanoformulations varied with silane surface modification. Within 98 h, only 8% of the total encapsulated PCA was released, suggesting sustained long-term release. We used nanoformulation solutions collected at days 3, 5, and 7 by disc diffusion or log reduction to evaluate their antibacterial effect against S. aureus. The hybrid nanoformulation showed efficient antibacterial and bactericidal effects that also depended on the surface modification and at a lower minimum inhibition concentration compared with the separate components. A hybrid nanoformulation of the PCA prodrug and ZnO NPs offers effective sustained-release inhibition of S. aureus growth.

Based on data from The Global Burden of Disease Study in 2016, dental and oral health problems, especially dental caries, are a disease experienced by almost half of the world’s population (3.58 billion people). One of the main causes of dental caries is the pathogenesis of Streptococcus mutans. Prevention can be achieved by controlling S. mutans using an antibacterial agent. The most commonly used antibacterial for the treatment of dental caries is chlorhexidine. However, long-term use of chlorhexidine has been reported to cause resistance and some side effects. Therefore, the discovery of a natural antibacterial agent is an urgent need. A natural antibacterial agent that can be used are herbal medicines derived from medicinal plants. Piper crocatum Ruiz and Pav has the potential to be used as a natural antibacterial agent for treating dental and oral health problems. Several studies reported that the leaves of P. crocatum Ruiz and Pav contain secondary metabolites such as essential oils, flavonoids, alkaloids, terpenoids, tannins, and phenolic compounds that are active against S. mutans. This review summarizes some information about P. crocatum Ruiz and Pav, various isolation methods, bioactivity, S. mutans bacteria that cause dental caries, biofilm formation mechanism, antibacterial properties, and the antibacterial mechanism of secondary metabolites in P. crocatum Ruiz and Pav.

Polymer nanocomposites based on polylactic acid (PLA) and graphene (Gr) were blended via melt blending and solution mixing. The properties of hardness and melt flow index (MFI) were investigated with variables of Gr loading from 0.5–2.0 wt.% and the effect of poly(ethylene glycol) (PEG) as plasticizer. The PLA/Gr nanocomposites exhibited higher hardness compared with neat PLA for both methods of nanocomposites preparation which were due to stiffness effect from nanofiller. The loading of PEG in the PLA nanocomposites resulted in the slightly decreasing of hardness. The hardness of PLA and PLA nanocomposites obtained from melt blending were higher than hardness from solution mixing where 2.0 wt.% Gr loading in PLA exhibited maximum value which was 83.1 Shore D. The significant improvement on the MFI could be seen with plasticizer loading compared to unfillled PEG in PLA blends obtained from both methods. Again, the MFI values of PLA/Gr showed from melt blending were higher than exhibited from solution blending method. The highest MFI was 70.6 g/10 min, obtained from 0.5 wt.% Gr loading in PLA/PEG/Gr nanocomposite. The morphology study from Field Emission Scanning Electron Microscopy (FESEM) analysis confirmed the interfacial interaction and homogeneity of Gr in PLA in order to enhance the hardness and MFI properties as discussed above.