Update on Chitin and Chitosan from Insects: Sources, Production, Characterization, and Biomedical Applications.

Insects, renowned for their abundant and renewable biomass, stand at the forefront of biomimicry-inspired research and offer promising alternatives for chitin and chitosan production considering mounting environmental concerns and the inherent limitations of conventional sources. This comprehensive review provides a meticulous exploration of the current state of insect-derived chitin and chitosan, focusing on their sources, production methods, characterization, physical and chemical properties, and emerging biomedical applications. Abundant insect sources of chitin and chitosan, from the Lepidoptera, Coleoptera, Orthoptera, Hymenoptera, Diptera, Hemiptera, Dictyoptera, Odonata, and Ephemeroptera orders, were comprehensively summarized. A variety of characterization techniques, including spectroscopy, chromatography, and microscopy, were used to reveal their physical and chemical properties like molecular weight, degree of deacetylation, and crystallinity, laying a solid foundation for their wide application, especially for the biomimetic design process. The examination of insect-derived chitin and chitosan extends into a wide realm of biomedical applications, highlighting their unique advantages in wound healing, tissue engineering, drug delivery, and antimicrobial therapies. Their intrinsic biocompatibility and antimicrobial properties position them as promising candidates for innovative solutions in diverse medical interventions.

Inspired by the Nature: A Post-printed Strategy to Efficiently Elaborate Parahydrophobic Surfaces.

The lack of drinkable water is one of the most significant risks for the future of the humanity. Estimates show that in the near future, this risk will become the origin of massive migrations leading to humanitarian disaster. As consequence, the development of solutions to provide water is becoming ever more critical, and a significant effort is devoted to identifying new sources of water. Among the developed strategies, fog harvesting, which takes advantage of atmospheric water to provide potable water, is a solution of interest due to its potential in sustainable development. Unfortunately, this approach suffers from low yield. In the present work, we take inspiration from living species to design and elaborate surfaces with high potential for water harvesting applications. This work takes advantage of 3D-printing and post-printing functionalization to elaborate a strategy that allows modelling, printing, and functionalization of surfaces to yield parahydrophobic behavior. The roughness and surface morphology of the prepared surfaces were investigated. These characteristics were then related to the observed wettability and potential of the functionalized interfaces for water harvesting applications. This work highlights significant variations in surface wettability via surface modification; strong hydrophobic behavior was observed via modification with linear carboxylic acids particularly for surfaces bearing vertical blades (plate with vertical blades and grid with vertical blades).

Investigation on dung beetle's (Heliocopris Hope, 1838) chitosan valorisation for hydrogel 3D printing.

Biopolymers and their derivatives are materials with increasing interest for industry and especially for sustainable engineering development. Among such kind of materials, carbohydrate polymer like highly deacetylated chitin (chitosan) is widely used for a wide range of applications, including material and biomedical developments. The majority of industrially produced chitosan is based on chitin extracted from crustacean exoskeleton. However, with increase of interest on this material, chitosan's production will rapidly become insufficient and other species should be investigated as new sources of chitosan. In the present work, we focus on the preparation of chitosan from giant dung beetles (Genus Heliocopris, Hope, 1838). This genus was chosen to show the possibility to take animals that develop and leave near dejection and valuate them for material applications. This work includes all the chitosan extraction procedures, chitosan characterisation IR, SEM, NMR, ash content, and deacetylation degree. Finally, the prepared carbohydrate polymer is used to form hydrogel. The prepared gel has been characterised and used for 3D printing, to show the compatibility of extracted chitosan with biomaterial application.

Bioinspired and Post-Functionalized 3D-Printed Surfaces with Parahydrophobic Properties.

Desertification is a growing risk for humanity. Studies show that water access will be the leading cause of massive migration in the future. For this reason, significant research efforts are devoted to identifying new sources of water. Among this work, one of the more interesting strategies takes advantage of atmospheric non-liquid water using water harvesting. Various strategies exist to harvest water, but many suffer from low yield. In this work, we take inspiration from a Mexican plant (Echeveria pulvinate) to prepare a material suitable for future water harvesting applications. Observation of E. pulvinate reveals that parahydrophobic properties are favorable for water harvesting. To mimic these properties, we leveraged a combination of 3D printing and post-functionalization to control surface wettability and obtain parahydrophobic properties. The prepared surfaces were investigated using IR and SEM. The surface roughness and wettability were also investigated to completely describe the elaborated surfaces and strongly hydrophobic surfaces with parahydrophobic properties are reported. This new approach offers a powerful platform to develop parahydrophobic features with desired three-dimensional shape.

Adsorption of Organic Dyes on Magnetic Iron Oxide Nanoparticles. Part I: Mechanisms and Adsorption-Induced Nanoparticle Agglomeration.

This series of two papers is devoted to the effect of organic dye (methylene blue, MB; or methyl orange, MO) adsorption on the surface of either bare or citrate-coated magnetic iron oxide nanoparticles (IONPs) on their primary agglomeration (in the absence of an applied magnetic field) and secondary field-induced agglomeration. The present paper (Part I) is focused on physicochemical mechanisms of dye adsorption and adsorption-induced primary agglomeration of IONPs. Dye adsorption to oppositely charged IONPs is found to be mostly promoted by electrostatic interactions and is very sensitive to pH and ionic strength variations. The shape of adsorption isotherms is correctly reproduced by the Langmuir law. For the particular MB/citrated IONP pair, the maximum surface density of adsorbed MB seems to correspond to the packing density of an adsorbed monolayer rather than to the surface density of the available adsorption sites. MB is shown to form H-aggregates on the surface of citrate-coated IONPs. The effective electric charge on the IONP surface remains nearly constant in a broad range of surface coverages by MB due to the combined action of counterion exchange and counterion condensation. Primary agglomeration of IONPs (revealed by an exponential increase of hydrodynamic size with surface coverage by MB) probably comes from correlation attractions or π-stacking aromatic interactions between adsorbed MB molecules or H-aggregates. From the application perspective, the maximum adsorption capacity is 139 ± 4 mg/g for the MB/citrated IONP pair (pH = 4-11) and 257 ± 16 mg/g for the MO/bare IONP pair (pH ∼ 4). Citrated IONPs have shown a good potential for their reusability in water treatment, with the adsorption efficiency remaining about 99% after nine adsorption/desorption cycles.

Investigation on Mecynorhina torquata Drury, 1782 (Coleoptera, Cetoniidae, Goliathini) cuticle: Surface properties, chitin and chitosan extraction.

Naturally derived polymers, such as cellulose or chitin, are materials with increasing interest for a sustainable future. Considering the pollution associated with plastics recycling, natural and fully biocompatible materials like cellulose and chitin are becoming increasingly more relevant for sustainable engineering applications. Chitin and highly deacetylated chitin (chitosan) are already implemented in a wide range of materials applications, especially in biomedical fields. One interesting aspect of chitin is that the majority of industrially produced chitin is extracted from shrimp exoskeleton. However, other arthropods can also be investigated as a source of chitin. In this work, we focus on the extraction of chitin and preparation of chitosan from a beetle specie: Mecynorhina torquata. This includes characterization of the native Mecynorhina torquata surfaces and all intermediate surfaces throughout the chitosan extraction procedure. The final product, prepared chitosan, is also characterized using IR, SEM, ash content, and deacetylation degree. In addition, spectacular iridescent surfaces of Mecynorhina torquata are highlighted at the intermediate steps during chitin extraction. Finally, as proof of concept, the isolated chitosan is used to form hydrogel.

Chitosan Extraction from Goliathus orientalis Moser, 1909: Characterization and Comparison with Commercially Available Chitosan.

Chitosan is a polymer obtained by deacetylation of chitin, and chitin is one of the major components of the arthropod cuticle. Chitin and chitosan are both polysaccharides and are considered to be an interesting class of biosourced materials. This is evident as chitosan has already demonstrated utility in various applications in both industrial and biomedical domains. In the present work, we study the possibility to extract chitin and prepare chitosan from the Goliath beetle Goliathus orientalis Moser. The presented work includes description of this process and observation of the macroscopic and microscopic variations that occur in the specimen during the treatment. The prepared chitosan is characterized and compared with commercially available chitosan using infrared and thermogravimetric analysis. The deacetylation degree of prepared chitosan is also evaluated and compared with commercially available shrimp chitosan.

Micro- and nanoscopic observations of sexual dimorphisms in Mecynorhina polyphemus confluens (Kraatz, 1890) (Coleoptera, Cetoniidae, Goliathini) and consequences for surface wettability.

In the animal kingdom, macroscopic variations in size, color, and even hairiness are frequently observed between male and female, making the sex of various species easy to discern. In the case of insects, similar variances also exist. While direct observation is a quick and efficient way to differentiate between sexes, there are also variations which are unseen to the naked eye and occur on a micro- or nanoscopic scale. Sometimes, these micro/nanoscopic variations can lead to significant variations in surface properties as a function of sex. Such is the case for the Mecynorhina polyphemus confluens (Kraatz, 1890). In this work, we characterize these micro- and nanoscale differences, and describe their impact on the surface properties (e.g. wettability). It is found that water interacts quite differently with the surface of the cuticle of Mecynorhina polyphenus confluens, depending on the specimen sex. On a female, water spreads readily across the elytra indicating hydrophilic behavior. However, on the surface of the male elytra, strong hydrophobicity is observed. Microscopic observations reveal differences in microscale surface morphology across the male and female cuticle. These observations contribute to a better, global understanding of the wettability behavior observed on M. polyphemus confluens.

Fabrication of Superhydrophobic Hierarchical Surfaces by Square Pulse Electrodeposition: Copper-Based Layers on Gold/Silicon (100) Substrates.

Copper based layers were fabricated on gold/silicon (100) substrates by using square pulse electrodeposition at different deposition temperatures. The predominant crystalline plane on Cu2 O samples at temperatures higher than 30 °C is (111), which is the most hydrophobic facet of Cu2 O cubic structure. Different crystallite structures such as semivertical leaves, fractal trees, and octahedral pyramids were formed on the surface. These water-repellent samples have hierarchical structures, including octahedral pyramid microstructures with small spherical balls on them and well-branched micrometric vertical leaves on the surface. They provide a suitable surface for trapping air pockets inside the structure and increasing the water contact angle up to 154°. This approach may be applicable to the large-scale preparation of water-repellent surfaces as superhydrophobicity can be achieved in a one-step deposition process without any secondary modifications.

Variation of Goliathus orientalis (Moser, 1909) Elytra Nanostructurations and Their Impact on Wettability.

Among the different species of flower beetles, there is one of particular notoriety: the Goliath beetle. This large insect can grow up to 11 cm long and is well-known for its distinctive black and white shield. In this paper, we focus on a particular Goliathus species: G. orientalis (Moser, 1909). We investigated the variations in properties of both the black and white parts of the upper face of G. orientalis; more precisely, the variation in surface properties with respect to the wettability of these two parts. This work reveals that the white parts of the shield have a higher hydrophobic character when compared to the black regions. While the black parts are slightly hydrophobic (θ = 91 ± 5°) and relatively smooth, the white parts are highly hydrophobic (θ = 130 ± 3°) with strong water adhesion (parahydrophobic); similar to the behavior observed for rose petals. Roughness and morphology analyses revealed significant differences between the two parts, and, hence, may explain the change in wettability. The white surfaces are covered with horizontally aligned nanohairs. Interestingly, vertically aligned microhairs are also present on the white surface. Furthermore, the surfaces of the microhairs are not smooth, they contain nanogrooves that are qualitatively similar to those observed in cactus spines. The nanogrooves may have an extremely important function regarding water harvesting, as they preferentially direct the migration of water droplets; this process could be mimicked in the future to capture and guide a large volume of water.

pH-Driven Wetting Switchability of Electrodeposited Superhydrophobic Copolymers of Pyrene Bearing Acid Functions and Fluorinated Chains.

A smart stimuli-responsive surface was fabricated by the electro-copolymerization of pyrene monomers followed by base and acid treatment. Copolymers of pyrenes bearing fluorinated chains (Py-nF6 ) and acid functions (Py-COOH) were produced with different molar concentrations of each monomer (0, 25, 50, 75, and 100 % of Py-nF6 vs. Py-COOH) by an electrochemical process. Two different perfluorinated pyrenes containing ester and amide groups were used to reach superhydrophobic properties. The relation of those bonds with the final properties of the surface was explored. The pH-sensitive group of Py-COOH allowed the surfaces to be reversibly switched from superhydrophobic (water contact angle>θw >150° and very low hysteresis) to hydrophilic (θw <90°). The amide and ester bonds influenced the recovery of the original wettability after both base and acid treatment. Although the fluorinated homopolymer with ester bonds was insensitive to base and acid treatment due to its superhydrophobic properties with ultralow water adhesion, the recovery of the original wettability for the copolymers was much more important with amide bonds due to the amide functional groups be more resistant to the hydrolysis reaction. This strategy offered the opportunity to access superhydrophobic films with switchable wettability by simple pH treatment. The films proved to be a good tool for use in biological applications, for example, as a bacterial-resistant film if superhydrophobic and as a bacterial-adherent film if hydrophilic.

Electrodeposited Poly(thieno[3,2-b]thiophene) Films for the Templateless Formation of Porous Structures by Galvanostatic and Pulse Deposition.

The formation of porous nanostructures by using a templateless electropolymerization process with thieno[3,2-b]thiophene as a monomer and two different deposition methods (galvanostatic and pulse potentiostatic deposition) has been studied. The wettability, roughness, and morphology of the surfaces are reported. The surfaces prepared by galvanostatic deposition show hydrophilic behavior (θw ≈80°) that is highly dependent on the roughness. Nanoseeds were formed in the first instances followed by the formation of large microcapsules and hollow spheres. Indeed, as the deposition time and current density increase, the size and amount of structures also increase. By pulse deposition, the surfaces are hydrophobic (θw ≈100°) and only show a roughness dependence if the mean surface roughness is >1.5 µm. The surfaces are formed from nanodomes and nanospheres, but they are less structured than that of surfaces produced by the galvanostatic method. The formation of these structures is directly related to the amount of gas released from trace water in situ during electropolymerization, which is highly dependent on the electrochemical method chosen. The formation of new seeds is highly favored by the galvanostatic method, whereas their growth is favored by the pulse deposition method. This is the first study on the use of galvanostatic and pulse deposition methods, with potential applications in surface chemistry. Thieno[3,2-b]thiophene proved to be very versatile to form different structures with potential applications as water harvesting and separation membranes.

Bifunctionalized Monomers for Surfaces with Controlled Hydrophobicity.

The control of surface wettability is a key parameter for many application fields (materials, biomedical engineering, etc.). In this work, a new and efficient strategy to synthesize monomers suitable for hydrophobic surface elaboration is reported. This original approach allows the preparation of monomers and, as a consequence, surfaces bearing two different substituents by using the Staudinger reductive amination and amidification. Rough conducting polymer films were prepared by electropolymerization. The original surfaces reported here are highly structured surfaces with tunable hydrophobic features. Depending on the grafted chains, the surfaces are hydrophilic (PEDOT-Benz-Ph, θ=80 °; PEDOT=poly(3,4-ethylenedioxythiophene)), hydrophobic (PEDOT-Benz-C12 , θ=132 °), or even superhydrophobic (PEDOT-Benz-F8 , θ=152 ° (α=5.0 °, H=0.3 °).

Switchable Surface Wettability by Using Boronic Ester Chemistry.

Here, we report for the first time the use of a boronic ester as an efficient tool for reversible surface post-functionalization. The boronic ester bond allows surfaces to be reversibly switched from hydrophilic to hydrophobic. Based on the well-known boronic acid/glycol affinity, this strategy offers the opportunity to play with surface hydrophobic properties by adding various boronic acids onto substrates bearing glycol groups. The post-functionalization can then be reversed to regenerate the starting glycol surface. This pathway allows for the preparation of various switchable surfaces for a large range of applications in biosensors, liquid transportation, and separation membranes.

Staudinger Vilarassa reaction: A powerful tool for surface modification and superhydrophobic properties.

Here we report for the time, the use of Staudinger-Vilarrasa reaction for fast surface functionalization. Using poly(3,4-ethylenedioxythiophene) nanofibrous surfaces bearing azido groups, this reaction allows for the functionalization of surfaces with amide linker in just 3 h. The functionalization by long alkyl chains induces the formation of highly hydrophobic surfaces while the surface structures are preserved. This reaction can be a key pathway for fast surface modification for a large range of applications such as in cell or bacterial adhesion, for example.

Azidomethyl-EDOT as a Platform for Tunable Surfaces with Nanostructures and Superhydrophobic Properties.

We report for the first time the use of click chemistry both to modify the surface morphology and to obtain superhydrophobic properties. Using click chemistry as a postfunctionalization of poly(3,4-ethylenedioxythiophene) nanofibers bearing azido groups, we show that the nanostructures already present on the surface as well as the surface hydrophobicity are highly affected by the used alkyne. These results allow one to envisage widely varied strategies to modify nanostructured surfaces while introducing various functions, for example to produce biosensors or antibacterial surfaces.

Formulation of highly functionalizable DNA nanoparticles based on 1,2-dithiolane derivatives.

We describe the formulation of synthetic virus models based on ionic compounds bearing the polymerizable 1,2-dithiolane moiety. First, cationic amphiphiles containing the polymeric inducer were prepared and used to efficiently condense a DNA plasmid (pDNA) into a highly monodisperse population of small polymeric cationic DNA nanoparticles (NPs; Dh ∼100 nm). These nonspecific cationic particles were then functionalized with anionic PEGylated conjugates, also based on the 1,2-dithiolane motifs, in order to produce stable and fully dispersible stealth DNA nanoparticles. Our results show that both ionic interactions and polymerization based on the 1,2-dithiolane pattern occur and that they produce highly functionalizable nonviral DNA NPs.

Step-by-Step Layer-by-Layer Assembly Using 1,2,3-Triazole as a Platform for Controlled Multicharged and Multifunctional Coatings.

Reported for the first time is the use of click chemistry to make layer-by-layer multiple post-functionalization treatments. The use of triazole as a platform for the post-functionalization allows the introduction of new clickable structures on the surface. The layer-by-layer strategy by means of click chemistry allows the introduction of both multiple and/or different consecutive modifications on the surface and multicharged species. Herein it consists of the use of molecules functionalized by a 1-azido group and propargyl bromide to deposit functionalized triazolium-type charged oligomers on the substrate. Moreover, different functional groups can be introduced at each step, which amplifies the use of this strategy for many potential applications. Here, to give an example of applications, that strategy is used to introduce alkyl chains and obtain highly hydrophobic materials. Moreover, it is shown that the surface morphology can also change after each treatment.

In vivo characterization of dynein-driven nanovectors using Drosophila oocytes.

Molecular motors transport various cargoes including vesicles, proteins and mRNAs, to distinct intracellular compartments. A significant challenge in the field of nanotechnology is to improve drug nuclear delivery by engineering nanocarriers transported by cytoskeletal motors. However, suitable in vivo models to assay transport and delivery efficiency remain very limited. Here, we develop a fast and genetically tractable assay to test the efficiency and dynamics of fluospheres (FS) using microinjection into Drosophila oocytes coupled with time-lapse microscopy. We designed dynein motor driven FS using a collection of dynein light chain 8 (LC8) peptide binding motifs as molecular linkers and characterized in real time the efficiency of the FS movement according to its linker's sequence. Results show that the conserved LC8 binding motif allows fast perinuclear nanoparticle's accumulation in a microtubule and dynein dependent mechanism. These data reveal the Drosophila oocyte as a new valuable tool for the design of motor driven nanovectors.

From Brittle to Pliant Viscoelastic Materials with Solid State Linear Polyphosphonium - Carboxylate Assemblies.

A polystyrenylphosphonium polymer was synthesized and complexed with various carboxylic acid derivatives to form new solid-state polyelectrolyte-surfactant assemblies. The properties of these ionic materials were highly dependent on the nature of the anion and included a brittle material, a rubbery ball that bounces, or a sticky fiber. The values for the equilibrium modulus, storage modulus, and loss modulus were dependent on the composition of the carboxylic acid and the number of electrostatic interactions. Small-angle X-ray scattering studies on the supramolecular assemblies confirmed a bilayer structure for two of the assemblies.