Copper nanoparticles (CuNPs) can be synthesized by green methods using plant extracts. These methods are more environmentally friendly and offer improved properties of the synthesized NPs in terms of biocompatibility and functional capabilities. Traditional medicine has a rich history of utilization of herbs for millennia, offering a viable alternative or complementary option to conventional pharmacological medications. Plants of traditional herbal use or those with medicinal properties are candidates to be used to obtain NPs due to their high and complex content of biocompounds with different redox capacities that provide a dynamic reaction environment for NP synthesis. Other synthesis conditions, such as salt precursor concentration, temperature, time synthesis, and pH, have a significant effect on the characteristics of the NPs. This paper will review the properties of some compounds from medicinal plants, plant extract obtention methods alternatives, characteristics of plant extracts, and how they relate to the NP synthesis process. Additionally, the document includes diverse applications associated with CuNPs, starting from antibacterial properties to potential applications in metabolic disease treatment, vegetable tissue culture, therapy, and cardioprotective effect, among others.

Metamaterials are broadly defined as artificial, electromagnetically homogeneous structures that exhibit unusual physical properties that are not present in nature. They possess extraordinary capabilities to bend electromagnetic waves. Their size, shape and composition can be engineered to modify their characteristics, such as iridescence, color shift, absorbance at different wavelengths, etc., and harness them as biosensors. Metamaterial construction from biological sources such as carbohydrates, proteins and nucleic acids represents a low-cost alternative, rendering high quantities and yields. In addition, the malleability of these biomaterials makes it possible to fabricate an endless number of structured materials such as composited nanoparticles, biofilms, nanofibers, quantum dots, and many others, with very specific, invaluable and tremendously useful optical characteristics. The intrinsic characteristics observed in biomaterials make them suitable for biomedical applications. This review addresses the optical characteristics of metamaterials obtained from the major macromolecules found in nature: carbohydrates, proteins and DNA, highlighting their biosensor field use, and pointing out their physical properties and production paths.

A trend has been established concerning the research and development of various green and biodegradable plastics for multi-purpose applications, aiming to replace petroleum-based plastics. Herein, we report the synthesis of chitosan (CH) films using lemon juice; these were reinforced with NiZnFe₂O₄ nanoparticles (NiZnFe₂O₄ NPs) to obtain improved mechanical and barrier properties, facilitating their future application as sustainable, corrosion-resistant coatings for medical instruments. The synthesized NiZnFe₂O₄ NPs had a crystallite size of ~29 nm. Reinforcement with the nanoparticles in bio-sourced chitosan films was conducted at two concentrations: 1% and 2%. The mechanical strength of the CH film was found to be 1.52 MPa, while the 2% NiZnFe₂O₄ NP-containing films showed stress-bearing potential of 1.04 MPa with a larger strain value, confirming the elastic nature of the films. Furthermore, the % elongation was directly proportional to the NP concentration, with the highest value of 36.833% obtained for the 2% NP-containing films. The CH films presented improved barrier properties with the introduction of the NiZnFe₂O₄ NPs, making them promising candidates for coatings in medical instruments; this could protect such instruments from corrosion under controlled conditions. This approach not only broadens the application range of biopolymeric films but also aligns with global sustainability goals, serving to reduce the reliance on non-renewable corrosion-resistant coatings.

Currently, there is a rush to develop green polymeric films such as biodegradable chitosan (CH) films to control and prevent plastic pollution from degrading the environment. This study reports a novel and sustainable green approach to the development of CH films using lemon juice (LJ) and lemon peel extract (LPE), the latter to dilute the LJ. The LPE was also utilized for the synthesis of ZnFe₂O₄ nanoparticles (NPs), adding to this work’s novelty. The crystalline size of the ZnFe₂O₄ NPs was computed to be ~16 nm. The introduction of 1% and 2% ZnFe₂O₄ NPs improved not only the mechanical properties of the films, but also their barrier properties and water solubility (WS). The tensile strength increased from 0.641 MPa to 0.835 MPa when 2% NPs were incorporated, which is almost 1.30 times greater; the NPs also enhanced the surface strength by 2.66 times, which was demonstrated by the puncture strength. The introduction of NPs occupied the vacant spaces and improved the barrier capabilities of the CH film by reducing the water vapor permeability (WVP) value from 8.752 ± 0.015 for bare CH films to 6.299 ± 0.009 for 2% NP-containing CH films. Overall, the introduction of ZnFe₂O₄ NPs boosted the mechanical and barrier properties of the CH films, and offers a promising method for developing sustainable, eco-friendly, and biodegradable polymeric films for potential packaging and medical applications to contribute to circular economic efforts.

Hericium erinaceus, an edible and medicinal mushroom, supports beneficial activities connected to brain and nerve health by accelerating the creation of new neurons and prevents the progression of neurodegenerative illnesses due to its bioactive components like erinacine A. H. erinaceus extract was used as a green synthesis reducing agent to generate silver nanoparticles (AgNPs). H. erinaceus was cultivated in an inoculated solid wheat medium for 52 days at 25 °C to produce biomass for extraction. The extraction was performed by ultrasonication (HeeUs) or microwave heating (HeeMw) using ethanol 96% as a dispersant. Once the H. erinaceus extracts (Hee’s) were obtained, each was mixed with an AgNO₃ solution to complete the NPs biosynthesis. The synthesized Hee derived nanoparticles (Hee-AgNPs) were characterized using DLS, FTIR, and HR-SEM, and were employed to analyze their antimicrobial, biocompatibility, and anti-protein aggregation properties. We determined the size, composition and morphology of the Hee-AgNPs. AgNPs synthesized by HeeUs had slightly better NPs basic properties. In a biocompatibility assay with erythrocytes, the hemolysis percentage results revealed a biocompatible nature of Hee-AgNPs. Additionally, Hee-AgNPs presented antimicrobial capacity against Escherichia coli, Bacillus subtilis, Serratia marcescens, Samonella thyphi, and Staphylococcus aureus. Accordingly, Hee-AgNPs showed a tendency to disintegrate synthetic protein aggregates, which are related to amyloid fibers. The cultivation and extraction methods of H. erinaceus successfully produced bioactive compounds that facilitated the synthesis of silver nanoparticles, HeeUs-AgNPs and HeeMw-AgNPs. While both exhibited significant antibacterial activity and biocompatibility, HeeUs-AgNPs demonstrated superior morphological characteristics and enhanced biocomponent content, confirming their potential for biomedical applications, including the prevention and disassembly of synthetic amyloid fibers. Graphical abstract