RSC Advances · 7 authors, 6 centres
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This review article summarizes the current advances in green nanobiopolymers—such as cellulose, chitin, lignin, and starch—for ecological applications. It covers their sources, synthesis methods (e.g., high-pressure homogenization, acid hydrolysis, ultrasonication), and structural characterization. The clinical significance is indirect, as the paper focuses on environmental sustainability and industrial/medical material applications rather than direct patient care.
**Background:** The review addresses the need to minimize reliance on non-renewable resources and reduce environmental pollution by exploiting biodegradable, low-toxicity, and abundant green nanobiopolymers. It highlights that conventional petroleum-based polymers contribute to plastic waste and environmental harm, motivating the development of bio-based alternatives from natural sources such as plants and microorganisms. The paper aims to coordinate recent outputs on nanobiopolymers, including their synthesis, structural characterization, and potential future utilization in a circular economy.
**Methods:** This is a narrative review article. The authors discuss multiple synthesis and processing techniques for various biopolymers. For nanocellulose, methods include pre-treatment (e.g., cell exfoliation, pulping, enzymatic treatment, oxidation), high-pressure homogenization (operating at 50–2000 MPa), microfluidization (up to 40,000 psi, approximately 276 MPa), crushing (using a grindstone at about 1500 rpm), cryocrushing (freezing in liquid nitrogen followed by crushing), high-intensity ultrasonication (HIUS), and destructive hydrolysis using mineral acids (sulfuric, hydrochloric, phosphoric, etc.). For chitin, extraction involves selection of shells, washing, drying, crushing, dilute hydrochloric acid treatment to remove calcium carbonate, alkali treatment (20% sodium hydroxide) to remove protein, and ethanol extraction of carotenoids. Lignin processing methods discussed include sulfite, kraft, and modern processes. Starch nanocrystals are produced via destructive hydrolysis at 35–45 °C. Nanoencapsulation methods include coaxial electrospinning and oil/water emulsification. Hydrogel synthesis involves crosslinking of polymer chains via covalent bonds or physical interactions (electrostatic hydrogen bonding, van der Waals forces).
**Key Results:** The paper reports specific numerical data from cited studies rather than original experiments. Cellulose content in plants is typically 33%, with cotton containing 90% cellulose and wood containing half or more. Chitin content in crab and shrimp shell garbage ranges from 8–33%. Chitin microfibril size is 2.5–2.8 nm. Starch granules have diameters varying from 2 to 100 μm depending on plant source, with density of 1.5 kg m⁻¹. Most starch varieties contain 72–82% amylose and 18–28% amylopectin. Starch nanocrystals have platelet-like shapes 5–7 nm thick with widths of 15–40 nm. Potato starch nanocrystals range from 40–100 nm. Starch particle size can be reduced from 3–6 μm to 10–20 nm via homogenization at 20 ps. Chitin whiskers at 2.96 wt% in PVA films produced excellent stiffness. PLA composites with 30 wt% Kenaf fiber showed improved mechanical properties. PLA/SEB (steam-exploded bamboo) composites showed double the strength and solidity of PLA alone. PLA compounds showed a 38% weight decrease after 25 days of biodegradation. Lignin-containing nanofibers exhibited over 70% cancer prevention activity, while pure PLLA nanofibers achieved only 15.5 ± 6.2% free radical scavenging after 72 hours. The crystallinity of commercial chitin was 97.9%, reduced to 88.0% after enzymatic treatment. Lignin molecular mass ranges from 1000 to 20,000 g mol⁻¹.
**Clinical Implications:** The clinical implications are indirect. The review suggests that green nanobiopolymers have potential applications in medical fields including wound dressing (chitin), tissue engineering (lignin-based nanofibers, hydrogels), drug delivery systems (targeted delivery using polymeric nanocomposites), and biosensors. Chitin is noted for use as a wound dressing material. Lignin-based nanofibers are proposed as biomaterials to reduce oxidative stress in tissue damage. Starch-based materials are used in therapeutic fields as disintegrants and lubricants. The authors emphasize that synchronization of greener polymeric nanocomposites in targeted drug delivery systems could minimize adverse effects on human health. However, the paper primarily focuses on environmental and industrial applications rather than direct clinical outcomes.