Visco-elastic properties of chitosan–titania nano-composites

Identifying barriers to scaled-up production and commercialization of chitin and chitosan using green technologies: A review and quantitative green chemistry assessment

Chitosan (CHT) production from Chitin (CH) is a billion-dollar industry but is constrained by multi-step chemical extractions that are energy and wastewater-intensive. Numerous green recovery technologies (GRT)s have paved the path for sustainable extraction, however, these have not been adopted for scale-up or mainstream commercialization. Therefore, this review critically evaluates the chemical, biological, combined biological-chemical and GRTs for CH/CHT recovery on commercially important criteria such as yields, molecular properties, cost/gram, water & energy use and wastewater & GHG emissions to identify barriers that hinder (i) the scaled-up, cost-effective commodity production of CH/CHT using GRTs (ii) the preparation of CH/CHT standards and (iii) the successful pathway from CH/CHT recovery to commercialization of chitosan-based products, supporting United Nations Sustainable Development Goals (UN SDG)s, particularly SDG 12. To arrive at the data-driven assessment, techno-economic and green chemistry metrics such as PMI and E-factor were calculated. The industry-developed quantitative green chemistry evaluator DOZN™ was used to assess resource & energy efficiency and human & environmental health hazards for CHT production. Mechanochemistry was identified as a viable GRT based on the limited literature available for quantitative assessment, and increasing the yield from GRT processes was identified as key to improving economic performance while also reducing environmental impacts.

TiO2 incorporated into a blend of biopolymeric matrices improves film properties and affects the postharvest conservation of papaya fruits under UV light

This work investigated the properties of chitosan-cassava starch biopolymeric films containing nanometric photoactive TiO2 particles for use in postharvest conservation of papaya fruits under UV light at a temperature of 15 ± 1 °C and a relative humidity of 90 ± 1 % for 24 days. Starch-chitosan blend films showed intermediate hydrophobicity and improved mechanical properties. The addition of 1 % TiO2 into the polymeric matrix of starch/chitosan (1:1) further improved the mechanical properties with solubility of 16.04 ± 0.41 %, visible transmittance of 31.76 ± 1.58 %, and reduced UV transmittance of more than 97 %. However, the addition of TiO2 exceeding 1 % led to the formation of agglomerates and excessive reduction in film transparency. UV exposure damaged the fruit peel and resulted in a higher weight loss. In contrast, the addition of 1 % TiO2 to the blend reduced the weight loss in light and dark by 7.12 ± 1.57 % and 5.27 ± 0.31 % respectively, and delayed fruit ripening.

Recent trends in polysaccharide-based biodegradable polymers for smart food packaging industry

Artificial packaging materials, such as plastic, can cause significant environmental problems. Thus, the use of polysaccharide-based biodegradable polymers (cellulose, starch, and alginate) has the potential in the field of environmental sustainability, reprocessing, or protection of the environment. Morphological and structural alterations caused by material degradation have a substantial impact on polymer material characteristics. To avoid degradation during storage, it is critical to evaluate and comprehend the structure, characteristics, and behavior of modern bio-based materials for potential food packaging applications. Hence, this review focused on the various types of polysaccharide-based biodegradable polymers (cellulose, starch, and alginate), their properties, and their commercial potential for food packaging applications. In addition, we overviewed the recent development of polysaccharide-based biodegradable polymer (cellulose, starch, and alginate) packaging for food products. The review concluded that the membrane and chromatographics are widely used in production of cellulose, starch, and alginate-based biodegradable polymers. Also, nanotechnology-based food packaging is widely used to improve the properties of cellulose, starch, and alginate biodegradable polymers and the incorporation of active agents to enhance the shelf life of food products. Overall, the review highlighted the potential of cellulose, starch, and alginate biodegradable polymers in the food packaging industry and the need for potential research and development to improve their properties and commercial viability.

Eco-design and tunable structure-properties of chitosan-epoxy-glycerol-silicate biohybrids using integrated crosslinking

Tunable structure-properties were achieved for chitosan-epoxy-glycerol-silicate (CHTGP) biohybrids, eco-designed via integrated amine-epoxy and waterborne sol-gel crosslinking reactions. Medium molecular weight chitosan (CHT), with 83 % degree of deacetylation was prepared by microwave-assisted alkaline deacetylation of chitin. The amine group of chitosan was covalently bonded to the epoxide of 3-glycidoxypropyltrimethoxysilane (G) for further crosslinking with a sol-gel derived glycerol-silicate precursor (P) from 0.5 % to 5 %. The impact of crosslinking density on the structural morphology, thermal, mechanical, moisture-retention and antimicrobial properties of the biohybrids were characterized by FTIR, NMR, SEM, swelling and bacterial inhibition studies and contrasted with a corresponding series (CHTP) without epoxy silane. Water uptake was significantly reduced in all biohybrids with a 12 % window of variation between the two series. Properties observed in biohybrids with only epoxy-amine (CHTG) or sol-gel crosslinking reactions (CHTP), were reversed in the integrated biohybrids (CHTGP) to impart improved thermal and mechanical stability and antibacterial activity.

Asenic removal from groundwater using granular chitosan-titanium adsorbent

Arsenic (As) contamination poses an urgent environmental risk, and its removal from groundwater remains a challenge due to the lack of efficient adsorbents. Herein, a novel granular chitosan-titanium (CS-Ti) adsorbent was fabricated by the sol-gel method. Batch experiments show that As(V) adsorption on CS-Ti followed the pseudo-second-order kinetic model, and the adsorption isotherm conformed to the Freundlich model with the correlation coefficient of 0.99. In situ FTIR spectra revealed that the CS-Ti adsorbent was composed of amorphous TiOx and chitosan by forming C-O-Ti and N-Ti bonds, and the amorphous TiOx was responsible for As(V) adsorption. Rapid small-scale column tests show that 165.6 μg/L of As in groundwater were effectively removed in approximately 126-bed volumes, and the spent adsorbents were regenerated with 0.01 mol/L NaOH and maintained the adsorption efficiency after four cycles. This study provides a simple and practical route to fabricate adsorbents for water treatment.

Heterogeneous Hybrid Nanocomposite Based on Chitosan/Magnesia Hybrid Films: Ecofriendly and Recyclable Solid Catalysts for Organic Reactions

Chitosan/magnesia hybrid films (CS-Mg) have been prepared via sol-gel process and employed as heterogeneous catalysts. An in situ generation of a magnesia network in the chitosan matrix was performed through hydrolysis/condensation reactions of magnesium ethoxide. The synthesized hybrid films were characterized using various analytical techniques, such as X-ray photo-electron spectroscopy (XPS), field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM). The hybrid films display excellent catalytic activities in Michael and Knoevenagel reactions via one pot or solvent-free approaches under microwave irradiation conditions. Chitosan/magnesia hybrid films, catalysed pyrimidine, benzochromene, coumarin and arylidene-malononitriles derivatives formation reactions occurred with highly efficient yields of 97%, 92%, 86% and 95% respectively. Due to the fact that the films are durable and insoluble in common organic solvents, they were easily separated and can be recycled up to five times without a considerable loss of their catalytic activity.

Na-Influenced Bulk and Surface Properties of the So-Called Iota(ι)-Alumina: Spectroscopy and Microscopy Studies

The test alumina (the so-called ι-Al₂O₃) was thermally recovered at 1,100°C from chitosan-AlO_x hybrid films and found to contain Na and Ca impurity ions inherited from the parent chitosan. Two different modifications of pure alumina, namely, γ- and α-Al₂O₃, were adopted as control samples. The test and control aluminas were examined for 1) the bulk elemental constitution by atomic absorption spectroscopy (AAS), 2) the surface chemical composition by X-ray photoelectron spectroscopy (XPS), 3) the bulk phase composition by X-ray powder diffractometry (XRD), ex-situ Fourier-transform infrared spectroscopy (IR), and Laser Raman (LRa) spectroscopy, 4) the surface area, topography, and morphology by N₂ sorptiometry, and atomic force (AFM) and scanning electron microscopy (SEM), 5) the surface adsorptive interactions with pyridine and 2-propanol gas-phase molecules by in-situ IR spectroscopy of the adsorbed species, and 6) the surface catalytic interactions with 2-propanol gas-phase molecules by in-situ IR spectroscopy of the gas phase. Results obtained could clearly show that the test alumina (ι-Al₂O₃) is only hypothetically pure alumina since in reality its bulk structure is majored by mullite-type Na-aluminate (Na_0.67Al₆O_9.33/NaAlO₂) and minored by Na-β-alumina (Na_1.71Al₁₁O₁₇) and β-alumina (NaAl₁₁O₁₇). Consistently, observed Na-influenced modifications of the surface chemistry, topology, and morphology, as well as adsorptive and catalytic interactions with pyridine and 2-propanol gas-phase molecules, showed significant deviations from those exhibited by the control pure aluminas (γ- and α-Al₂O₃).

Antimicrobial activities of chitosan/titanium dioxide composites as a biological nanolayer for food preservation: A review

Packaging is an integral part of food industry that preserves the properties of food during storage. Food spoilage caused by foodborne microorganisms is a public health problem that imposes a significant burden on the healthcare systems. Moreover, packaging based on artificial and chemical materials such as plastic is destructive to the environment. Chitosan can be categorized as an active food packaging material because of its inherent antimicrobial properties and capacity to carry various active components. Combining chitosan and metallic nanoparticles can be used as a practical approach in antimicrobial packaging systems. This strategy has advantages of thermal stability, barrier properties, antioxidant and antimicrobial packaging. Titanium dioxide is one of these nanoparticles that plays a photocatalytic role by releasing reactive oxygen species, thereby leading to the destruction of microorganisms' cell wall and extension of food shelf life. This review elaborates on the antimicrobial applications of chitosan/titanium dioxide nanoparticles films in food packaging systems.

New insight into the role of crosslinkers and composition on selectivity and kinetics of antimony uptake by chitosan-titania composite beads

Role of composition and the nature of crosslinking on the properties of titania-chitosan beads have been investigated in detail. The investigations were done in order to explore the feasibility of design and synthesis of titania-chitosan beads with bespoke functionality based on the intended application. This would greatly enhance the potential for the industrial application of these biopolymer based beads. Beads of varying compositions (of titania and chitosan) were prepared and crosslinked using epichlorohydrin or glutaraldehyde. The physical characteristics and antimony binding properties of the resultant crosslinked titania-chitosan beads were investigated in detail. Influence of chitosan amount on swelling was seen to be more predominant in the glutaraldehyde crosslinked beads (TA-Cts-Glu). TA-Cts-Glu beads showed more swelling and better antimony (Sb(III) and Sb(V)) uptake as compared to the epichlorohydrin crosslinked beads (TA-CTS-Epi). While TA-Cts-Glu beads showed faster uptake kinetics compared to the TA-CTS-Epi beads, the latter showed selectivity towards Sb(III) against transition metal cations. Further, the beads exhibited differential uptake of Sb(V) and Sb(III). TA-Cts-Glu beads prepared with equal amounts of titania and chitosan showed the maximum Sb(V) uptake while the TA-Cts-Epi beads with higher chitosan to titania ratio showed the least. Sb(V) binding was enhanced by the crosslinked chitosan, while the Sb(III) uptake was aided predominantly by the titania content in the beads.

Biodegradable Films from Phytosynthesized TiO2 Nanoparticles and Nanofungal Chitosan as Probable Nanofertilizers

Titanium dioxide nanoparticles (TiO2-NPs) have great importance for plant nutrition and growth, at little concentrations. The bioactive polymer chitosan and its NPs provide outstanding characteristics for capping and enhancements of nanometals. The phytosynthesis of TiO2-NPswas promisingly achieved using an extract of pomegranate rind, whereas the fungal chitosan (FCt) was produced from Aspergillus brasiliensis biomass and was transformed to nanoform. The phytosynthesis of TiO2-NPs generated homogenous spherical particles with 13 to 64 nm range and 37 nm mean size. The extracted FCt had 92% deacetylation degree and a molecular weight of 28,400 Da. The infrared spectral analysis of TiO2-NPs, FCt-NPs, and their nanocomposite indicated their functional groups and biochemical interactions. The released amounts of TiO2-NPs from their nanocomposite with FCt–NPs were 31% and 50% after the first and third hour, respectively. The nanocomposite film had a faster hydrodegradability rate which resulted from TiO2-NP addition. Therefore, the fabricated nanocomposite from FCt/TiO2-NPs could have elevated potentiality for application as liquid spray for foliar feeding or as powder for soil amendment.

Chitosan-TiO2: A Versatile Hybrid Composite

In recent years, a strong interest has emerged in hybrid composites and their potential uses, especially in chitosan–titanium dioxide (CS–TiO₂) composites, which have interesting technological properties and applications. This review describes the reported advantages and limitations of the functionalization of chitosan by adding TiO₂ nanoparticles. Their effects on structural, textural, thermal, optical, mechanical, and vapor barrier properties and their biodegradability are also discussed. Evidence shows that the incorporation of TiO₂ onto the CS matrix improves all the above properties in a dose-dependent manner. Nonetheless, the CS–TiO₂ composite exhibits great potential applications including antimicrobial activity against bacteria and fungi; UV-barrier properties when it is used for packaging and textile purposes; environmental applications for removal of heavy metal ions and degradation of diverse water pollutants; biomedical applications as a wound-healing material, drug delivery system, or by the development of biosensors. Furthermore, no cytotoxic effects of CS–TiO₂ have been reported on different cell lines, which supports their use for food and biomedical applications. Moreover, CS–TiO₂ has also been used as an anti-corrosive material. However, the development of suitable protocols for CS–TiO₂ composite preparation is mandatory for industrial-scale implementation.

Synthesis of chitosan-ethylene glycol diglycidyl ether/TiO2 nanoparticles for adsorption of reactive orange 16 dye using a response surface methodology approach

Chitosan-ethylene glycol diglycidyl ether/TiO₂ nanoparticles (CS-EGDE/TNP) composite was synthesized to be biosorbent for the removal of reactive orange 16 (RO16) dye from aqueous solution. The CS-EGDE/TNP composite was characterized via BET, XRD, FTIR, and SEM-EDX techniques. Response surface methodology (RSM) with Box-Behnken design (BBD) was applied to optimize the adsorption key parameters such as adsorbent dose (A: 0.02-0.08 g/L), RO16 dye concentration (B: 20-80 mg/L), solution pH (C: 4-10), temperature (D: 30-50 °C), and contact time (E: 30-90 min). The adsorption isotherm followed Freundlich model and pseudo-second order (PSO) kinetic model. The adsorption capacity of CS-EGDE/TNP for RO16 dye was 1407.4 mg/g at 40 °C. The adsorption mechanism of RO16 dye on the surface of CS-EGDE/TNP can be attributed to various interactions such as electrostatic attraction, n-π interaction, Yoshida H-bonding, and H-bonding. Results supported the potential use of CS-EGDE/TNP as effective adsorbent for the treatment of acid reactive dye.

Daylight Bactericidal Titania Textiles: A Contribution to Nosocomial Infections Control

: Daylight bactericidal cotton (100% cotton) textiles are presented and proposed for future hospital use. Amorphous titania (a-TiO2) and amorphous titania/chitosan complexes (a-TiO2//CS) were the selected bactericidal agents. Nanoparticles (NPs) and films were the two paths designed. Cotton textiles were impregnated with a-TiO2-based NPs or coated with a-TiO2 films. Industrial impregnation/coating will be implemented during the textile finishing treatments. A novel (room temperature and base-catalyzed), green (hydrothermal water as a catalyst), time-saving, and easy scale-up sol-gel process was established to produce the a-TiO2-based NPs. Amorphous-TiO2 films were produced by a dip-in (acid catalyzed) sol-gel solution. The daylight bactericidal performance (without the need of an external ultraviolet light source) of a-TiO2 NPs, films, and impregnated/coated textiles was proven according to AATCC 100 and ASTM E2149, using Staphylococcus aureus (ATCC®6538TM) as the bacterial indicator strain. A bacterial reduction of 99.97% was achieved for the a-TiO2 films and of 99.97% for the a-TiO2/CS NPs. Regarding the impregnated textiles, a bacterial reduction of 91.66% was achieved with a-TiO2/CS NPs, and 99.97% for cotton textiles coated with an a-TiO2 film.

Nano-TiO2 Doped Chitosan Scaffold for the Bone Tissue Engineering Applications

The present focus is on the synthesis of highly effective, porous, biocompatible, and inert scaffold by using ceramic nanoparticles and natural polymer for the application in tissue engineering. Freeze-drying method was used to fabricate nano-TiO₂ doped chitosan sample scaffold. Nano-TiO₂/chitosan scaffold can considered as an effective solution for damaged tissue regeneration. The interaction between chitosan (polysaccharide) and nano-TiO₂ makes it highly porous and brittle that could be an effective substitute for bone tissue engineering. The TiO₂ nanoparticles have a great surface area and inert properties while chitosan is highly biocompatible and antibacterial. The physiochemical properties of TiO₂ nanoparticles and scaffold are evaluated by XRD and FTIR. The nanoparticles doped scaffold has given improved density (1.2870g/cm³) that is comparatively relevant to the dry bone (0.8 - 1.2 gm/cm³). The open and closed porosity of sample scaffold were measured by using Brunauer–Emmett–Teller analyzer (BET) and scanning electron microscopy (SEM). The mechanical properties are examined by stable microsystem (Texture Analyzer). The in vitro degradation of scaffold is calculated in PBS containing lysozyme at pH 7.4. Electron and fluorescence microscopy are used to study morphological characteristics of the scaffolds and TiO₂ nanoparticles. The growth factor and drug-loaded composites can improve osteogenesis and vascularization.

Antimicrobial, Optical and Mechanical Properties of Chitosan-Starch Films with Natural Extracts

Natural extracts possess several kinds of antioxidants (anthocyanins, betalains, thymol, carvacrol, and resveratrol) that have also demonstrated antimicrobial properties. In order to study these properties, extracts from cranberry, blueberry, beetroot, pomegranate, oregano, pitaya, and resveratrol (from grapes) were obtained. Growth inhibition tests of mesophilic aerobes, coliforms, and fungi were conducted in films prepared from the extracts in accordance with Mexican Official Norms (NOM). Optical properties such as transparency and opacity, mechanical properties, and pH were also analyzed in these materials. The films with beetroot, cranberry, and blueberry extracts demonstrated the best antimicrobial activity against various bacteria and fungi in comparison with unmodified chitosan–starch film. This study shows that the addition of antioxidants improved the antimicrobial performance of these films. It was also found that antimicrobial properties are inherent to the films. These polymers combined with the extracts effectively inhibit or reduce microorganism growth from human and environmental contact; therefore, previous sterilization could be unnecessary in comparison with traditional plastics. The presence of extracts decreased transmittance percentages at 280 and 400 nm, as well as the transparency values, while increasing their opacity values, providing better UV–VIS light barrier properties. Despite diminished glass transition temperatures (Tg), the values obtained are still adequate for food packaging applications.

A superhydrophilic and underwater superoleophobic chitosan–TiO2 composite membrane for fast oil-in-water emulsion separation

The CST modified membrane showed an excellent flux and can maintain underwater superoleophobicity in corrosive aqueous media.

Surface modification of TiO2 nanoparticles with biodegradable nanocellolose and synthesis of novel polyimide/cellulose/TiO2 membrane

In this paper, novel polyimide/cellulose/TiO₂ bionanocomposites (PI/BNCs) were prepared via a simple and inexpensive ultrasonic irradiation process. PI was synthesized by direct polycondensation reaction of novel monomer dianhydride with 4-(2-(4-aminophenyl)-1,1,1,3,3,3-hexafluoropropan-2-yl)benzenamine. Due to the high surface energy and tendency for agglomeration the surface of nanoparticles was modified with cellulose. PI/BNCs containing 5, 10, and 15% of cellulose/TiO₂ (BNCs) were successfully fabricated through ultrasonic irradiation technique. The obtained PI/BNCs were characterized by Fourier transform-infrared (FT-IR) spectroscopy, thermogravimetry analysis, X-ray powder diffraction, field emission-scanning electron microscopy (FE-SEM), and transmission electron microscopy (TEM). Thermogravimetric analysis data indicated an increase thermal stability of the PI/BNC polymers in compared to the pure polymer. From TEM image of PI/BNCs it can be found that the surface modified TiO₂ with diametric size of less than 50 nm, uniformly dispersed in the obtained PI matrix. The results obtained from gas permeation experiments with a constant pressure setup indicated that adding cellulose/TiO₂ to the polymeric membrane structure increased the permeability of the membranes.

An overview of chitin or chitosan/nano ceramic composite scaffolds for bone tissue engineering

Chitin and chitosan based nanocomposite scaffolds have been widely used for bone tissue engineering. These chitin and chitosan based scaffolds were reinforced with nanocomponents viz Hydroxyapatite (HAp), Bioglass ceramic (BGC), Silicon dioxide (SiO₂), Titanium dioxide (TiO₂) and Zirconium oxide (ZrO₂) to develop nanocomposite scaffolds. Plenty of works have been reported on the applications and characteristics of the nanoceramic composites however, compiling the work done in this field and presenting it in a single article is a thrust area. This review is written with an aim to fill this gap and focus on the preparations and applications of chitin or chitosan/nHAp, chitin or chitosan/nBGC, chitin or chitosan/nSiO₂, chitin or chitosan/nTiO₂ and chitin or chitosan/nZrO₂ in the field of bone tissue engineering in detail. Many reports so far exemplify the importance of ceramics in bone regeneration. The effect of nanoceramics over native ceramics in developing composites, its role in osteogenesis etc. are the gist of this review.

Fabrication, nanomechanical characterization, and cytocompatibility of gold-reinforced chitosan bio-nanocomposites

Chitosan, a naturally derived polymer represents one of the most technologically important classes of active materials with applications in a variety of industrial and biomedical fields. Gold nanoparticles (~32 nm) were synthesized via a citrate reduction method from chloroauric acid and incorporated in Chitosan matrix. Bio-nanocomposite films with varying concentrations of gold nanoparticles were prepared through solution casting process. Uniform distribution of gold nanoparticles was achieved throughout the chitosan matrix and was confirmed with SEM. Synthesis outcomes and prepared nanocomposites were characterized using SEM, TEM, EDX, SAED, UV-vis, XRD, DLS, and Zeta potential for their physical, morphological and structural properties. Nanoscale properties of materials under the influence of temperature were characterized through nanoindentation techniques. From quasi-static nanoindentation, it was observed that hardness and reduced modulus of the nanocomposites were increased significantly in direct proportion to the gold nanoparticle concentration. Gold nanoparticle concentration also showed positive impact on storage modulus and thermal stability of the material. The obtained films were confirmed to be biocompatible by their ability to support growth of human cells in vitro. In summary, the results show enhanced mechanical properties with increasing gold nanoparticle concentration, and provide better understanding of the structure-property relationships of such biocompatible materials for potential biomedical applications.

Fabrication and characterization of gold-nanoparticles/chitosan film: a scaffold for L929-fibroblasts

The objective of the present study was to fabricate a gold nanoparticle crosslinked chitosan (Ch/AuNPs) composite film simple and to evaluate its use as a carrier matrix for L929- fibroblasts. L929- fibroblasts were seeded either onto Ch or Ch/AuNPs scaffolds. The Ch/AuNPs scaffold exhibited a higher cell proliferation and growth rate. The cytotoxicity test determined trypan blue staining indicated that Ch scaffolds devoid of AuNPs expressed almost no toxicity while the Ch/AuNPs composite scaffolds expressed a very limited toxicity only at higher doses. The Ch/AuNPs scaffold promotes cell attachment, growth and proliferation with almost no cytotoxicity.