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<p>Shrimp shell biowaste offers a sustainable solution for waste management by enabling the production of valuable bio-based materials. The objectives of this study are to synthesize carboxylated chitosan nanocrystals (ChsNCs) from shrimp shell biowaste using reduced volumes of NaBH<sub>4</sub> and NaOH, to comprehensively characterize the synthesized ChsNCs, and to evaluate their antibacterial efficacy against selected bacterial strains. The synthesis involved demineralization, deproteinization, controlled oxidation, and carboxylation processes, resulting in ChsNCs with a yield of 14.71%. A comprehensive characterization of ChsNCs was conducted using SEM, EDX, FTIR, XRD, TGA, DTA, AFM, and DLS techniques. Antibacterial activity was evaluated against <i>Staphylococcus aureus</i>,<i> Enterococcus faecalis</i>,<i> Escherichia coli</i>,<i> and Klebsiella pneumoniae</i> using agar well diffusion and MIC assays. SEM and EDX analysis revealed a clustered morphology with increased surface roughness, and an elemental composition of 49.13% carbon, 46.98% oxygen, and 3.89% nitrogen. XRD showed a crystallinity index of 28.3%, indicating amorphization during deacetylation. TGA showed thermal degradation occurring between 200&#xa0;°C and 375&#xa0;°C, with DTA revealing exothermic peaks at 317.23&#xa0;°C and 375.82&#xa0;°C. AFM revealed fibrillar particles of 100–300&#xa0;nm in length and 15–35&#xa0;nm in width, while DLS showed a Z-average diameter of 144.8&#xa0;nm and a polydispersity index of 0.184 ± 0.006. The antibacterial assay indicated that effectiveness varies with concentration, with inhibition zones measuring between 16.25 ± 0.65&#xa0;mm and 28.15 ± 0.39&#xa0;mm, and significant p-values of <i>p</i> &lt; 0.05. Gram-negative bacteria showed greater susceptibility, with <i>E. coli</i> exhibiting the highest sensitivity. MIC values ranged from 0.78&#xa0;mg/mL for <i>E. faecalis</i> to 3.12&#xa0;mg/mL for <i>K. pneumoniae</i>, confirming broad-spectrum activity. These findings indicate the potential of ChsNCs in biomedical and environmental applications, providing a practical, cost-effective, and sustainable approach to developing nanomaterials from shrimp shell biowaste.</p> Graphical Abstract <p></p>

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Synthesis and Characterization of Carboxylated Chitosan Nanocrystals from Shrimp Shell Biowaste using Reduced Chemical Volume: Structural and Antibacterial Properties

  • 期刊论文

  • 发表日期：

    2026年1月16日

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  • Rumesh Samarawickrama,
  • Hafeezullah Memon,
  • Samudrika Wijayapala,
  • Annesly Nandana Fernando,
  • Geeshan Pasindu Bandara

摘要

Shrimp shell biowaste offers a sustainable solution for waste management by enabling the production of valuable bio-based materials. The objectives of this study are to synthesize carboxylated chitosan nanocrystals (ChsNCs) from shrimp shell biowaste using reduced volumes of NaBH4 and NaOH, to comprehensively characterize the synthesized ChsNCs, and to evaluate their antibacterial efficacy against selected bacterial strains. The synthesis involved demineralization, deproteinization, controlled oxidation, and carboxylation processes, resulting in ChsNCs with a yield of 14.71%. A comprehensive characterization of ChsNCs was conducted using SEM, EDX, FTIR, XRD, TGA, DTA, AFM, and DLS techniques. Antibacterial activity was evaluated against Staphylococcus aureus, Enterococcus faecalis, Escherichia coli, and Klebsiella pneumoniae using agar well diffusion and MIC assays. SEM and EDX analysis revealed a clustered morphology with increased surface roughness, and an elemental composition of 49.13% carbon, 46.98% oxygen, and 3.89% nitrogen. XRD showed a crystallinity index of 28.3%, indicating amorphization during deacetylation. TGA showed thermal degradation occurring between 200 °C and 375 °C, with DTA revealing exothermic peaks at 317.23 °C and 375.82 °C. AFM revealed fibrillar particles of 100–300 nm in length and 15–35 nm in width, while DLS showed a Z-average diameter of 144.8 nm and a polydispersity index of 0.184 ± 0.006. The antibacterial assay indicated that effectiveness varies with concentration, with inhibition zones measuring between 16.25 ± 0.65 mm and 28.15 ± 0.39 mm, and significant p-values of p < 0.05. Gram-negative bacteria showed greater susceptibility, with E. coli exhibiting the highest sensitivity. MIC values ranged from 0.78 mg/mL for E. faecalis to 3.12 mg/mL for K. pneumoniae, confirming broad-spectrum activity. These findings indicate the potential of ChsNCs in biomedical and environmental applications, providing a practical, cost-effective, and sustainable approach to developing nanomaterials from shrimp shell biowaste.

Graphical Abstract