The role of cellulose nanocrystals in biocompatible starch-based clicked nanocomposite hydrogels

Synthesis of thermally and pH-responsive poly(2-(dimethylamino)ethyl methacrylate)-based hydrogel reinforced with cellulose nanocrystals for sustained drug release

Hydrogels are widely employed in biomedical applications due to their high swelling potential, tailored mechanical properties, biocompatibility, and ability to incorporate drugs to modify their release behavior. This study explored the synthesis of dual stimuli-responsive composite hydrogels by combining poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) with 4, 8, and 12 % (w/w) of cellulose nanocrystals (CNC) through in-situ free-radical polymerization, modifying their properties for topical anti-inflammatory release. Although PDMAEMA-based hydrogels have been known for their responsiveness to pH and temperature stimuli, which are useful for modulating the release profile of drugs, their use as a matrix for anti-inflammatory topical applications remains unexplored. Thus, a comprehensive analysis of CNC concentration's impact on PDMAEMA-based hydrogel structure and physicochemical properties is provided. The incorporation of ibuprofen as an anti-inflammatory model was assessed, providing insights into the potential of these composite hydrogels for sustained drug delivery applications. Overall, the hydrogels exhibited homogenous CNC dispersion, with gel fraction higher than 70 % and ibuprofen load higher than 90 %. The rise in CNC concentration led to an increase hydrogel stiffness. Finally, the CNC incorporation also modified the ibuprofen release to a more sustained profile, following the Peppas-Sahlin model, which may be attractive for developing pharmaceutical devices for different therapeutical scenarios.

Synthetic and biopolymers-based antimicrobial hybrid hydrogels: a focused review

The constantly accelerating occurrence of microbial infections and their antibiotic resistance has spurred advancement in the field of material sciences and has guided the development of novel materials with anti-bacterial properties. To address the clinical exigencies, the material of choice should be biodegradable, biocompatible, and able to offer prolonged antibacterial effects. As an attractive option, hydrogels have been explored globally as a potent biomaterial platform that can furnish essential antibacterial attributes owing to its three-dimensional (3D) hydrophilic polymeric network, adequate biocompatibility, and cellular adhesion. The current review focuses on the utilization of different antimicrobial hydrogels based on their sources (natural and synthetic). Further, the review also highlights the strategies for the generation of hydrogels with their advantages and disadvantages and their applications in different biomedical fields. Finally, the prospects in the development of hydrogels-based antimicrobial biomaterials are discussed along with some key challenges encountered during their development and clinical translation.

Nanocomposite Hydrogels-A Promising Approach towards Enhanced Bioavailability and Controlled Drug Delivery

Nanotechnology has emerged as the eminent focus of today's research to overcome challenges related to conventional drug delivery systems. A wide spectrum of novel delivery systems has been investigated to improve the therapeutic outcomes of drugs. The polymer-based nanocomposite hydrogels (NCHs) that have evolved as efficient carriers for controlled drug delivery are of particular interest in this regard. Nanocomposites amalgamate the properties of both nanoparticles (NPs) as well as hydrogels, exhibiting superior functionalities over conventional hydrogels. This multiple functionality is based upon advanced mechanical, electrical, optical as well as magnetic properties. Here is a brief overview of the various types of nanocomposites, such as NCHs based on Carbon-bearing nanomaterials, polymeric nanoparticles, inorganic nanoparticles, and metal and metal-oxide NPs. Accordingly, this article will review numerous ways of preparing these NCHs with particular emphasis on the vast biomedical applications displayed by them in numerous fields such as tissue engineering, drug delivery, wound healing, bioprinting, biosensing, imaging and gene silencing, cancer therapy, antibacterial therapy, etc. Moreover, various features can be tuned, based on the final application, by controlling the chemical composition of hydrogel network, which may also influence the released conduct. Subsequently, the recent work and future prospects of this newly emerging class of drug delivery system have been enlisted.

A dual physical crosslinking starch-based hydrogel exhibiting high strength, fatigue resistance, excellent biocompatibility, and biodegradability

Simultaneous realization of high strength, toughness, and fatigue resistance in natural starch-based hydrogel materials is challenging. A facile method of in situ self-assembly and a freeze-thaw cycle was proposed to construct double-network nanocomposite hydrogels of debranched corn starch/polyvinyl alcohol (Gels). Rheology, chemical structure, microstructure, and mechanical property of Gels were investigated. Notably, short linear starch chains were self-assembled into nanoparticles and subsequently into 3D microaggregates, which were tightly wrapped by starch and PVA network. Compared with corn starch single-network and starch/PVA double-network hydrogels, the Gels reached up to a higher compressive strength (ca. 1095.7 kPa), and then achieved to ∼20-30-fold improvement in compressive strength. Recovery efficiency exceeded 85% after 20 successive compression loading-unloading cycle tests. Furthermore, the Gels had good biocompatibility to L929 cells. Hence, the high-performance starch hydrogels are thought to serve as a biodegradable and biocompatible material to replace synthetic hydrogels, which can broaden their application fields.

Cellular infiltration in an injectable sulfated cellulose nanocrystal hydrogel and efficient angiogenesis by VEGF loading

BACKGROUND

Cellular infiltration and angiogenesis into implanted biomaterial scaffolds are crucial for successful host tissue integration and tissue regeneration. Cellulose nanocrystal (CNC) is a nano-sized cellulose derivative, which can form an injectable physical gel with salts. Sulfate groups of sulfated CNC (CNC-S) can act as a binding domain to various growth factors and cytokines with a heparin-binding domain for sustained release of them. Vascular endothelial growth factor (VEGF) can promote the proliferation of endothelial cells and angiogenesis. In this study, VEGF-loaded CNC-S hydrogel was evaluated as an injectable scaffold that can induce cellular infiltration and angiogenesis.

METHODS

CNC-S was hydrolyzed to get desulfated CNC (CNC-DS), which was used as a negative control group against CNC-S. Both CNC-S and CNC-DS hydrogels were prepared and compared in terms of biocompatibility and VEGF release. The hydrogels with or without VEGF loading were subcutaneously injected into mice to evaluate the biocompatibility, cellular infiltration, and angiogenesis induction of the hydrogels.

RESULTS

Both hydrogels possessed similar stability and shear-thinning behavior to be applicable as injectable hydrogels. However, CNC-S hydrogel showed sustained release (until 8 weeks) of VEGF whereas CNC-DS showed a very fast release of VEGF with a large burst. Subcutaneously injected CNC-S hydrogel showed much enhanced cellular infiltration as well as better biocompatibility with milder foreign body response than CNC-DS hydrogel. Furthermore, VEGF-loaded CNC-S hydrogel induced significant angiogenesis inside the hydrogel whereas VEGF-loaded CNC-DS did not.

CONCLUSION

CNC-S possesses good properties as a biomaterial including injectability, biocompatibility, and allowing cellular infiltration and sustained release of growth factors. VEGF-loaded CNC-S hydrogel exhibited efficient angiogenesis inside the hydrogel. The sulfate group of CNC-S was a key for good biocompatibility and the biological activities of VEGF-loaded CNC hydrogel.

Preparation, Characterization and Antibacterial Property Analysis of Cellulose Nanocrystals (CNC) and Chitosan Nanoparticles Fine-Tuned Starch Film

To improve the mechanical and antibacterial properties of traditional starch-based film, herein, cellulose nanocrystals (CNCs) and chitosan nanoparticles (CS NPs) were introduced to potato starch (PS, film-forming matrix) for the preparation of nanocomposite film without incorporation of additional antibacterial agents. CNCs with varied concentrations were added to PS and CS NPs composite system to evaluate the optimal film performance. The results showed that tensile strength (TS) of nanocomposite film with 0, 0.01, 0.05, and 0.1% (w/w) CNCs incorporation were 41, 46, 47 and 41 MPa, respectively. The elongation at break (EAB) reached 12.5, 10.2, 7.1 and 13.3%, respectively. Due to the reinforcing effect of CNCs, surface morphology and structural properties of nanocomposite film were altered. TGA analysis confirmed the existence of hydrogen bondings and electrostatic attractions between components in the film-forming matrix. The prepared nanocomposite films showed good antibacterial properties against both E. coli and S. aureus. The nanocomposite film, consist of three most abundant biodegradable polymers, could potentially serve as antibacterial packaging films with strong mechanical properties for food and allied industries.

Thermoplastic starch nanocomposites: sources, production and applications - a review

The development of materials based on thermoplastic starch (TPS) is an excellent alternative to replace or reduce the use of petroleum-derived polymers. The abundance, renewable origin, biodegradability, biocompatibility, and low cost of starch are among the advantages related to the application of TPS compared to other thermoplastic biopolymers. However, through the literature review, it was possible to observe the need to improve some properties, to allow TPS to replace commonly used polyolefins. The studies reviewed achieved these modifications were achieved by using plasticizers, adjusting processing conditions, and incorporating fillers. In this sense, the addition of nanofillers proved to be the main modification strategy due to the large number of available nanofillers and the low charge concentration required for such improvement. The improvement can be seen in thermal, mechanical, electrical, optical, magnetic, antimicrobial, barrier, biocompatibility, cytotoxicity, solubility, and swelling properties. These modification strategies, the reviewed studies described the development of a wide range of materials. These are products with great potential for targeting different applications. Thus, this review addresses a wide range of essential aspects in developing of this type of nanocomposite. Covering from starch sources, processing routes, characterization methods, the properties of the obtained nanocomposites, to the various applications. Therefore, this review will provide an overview for everyone interested in working with TPS nanocomposites. Through a comprehensive review of the subject, which in most studies is done in a way directed to a specific area of study.

Diels-Alder Cycloaddition Reactions in Sustainable Media

Diels-Alder cycloaddition reaction is one of the most powerful strategies for the construction of six-membered carbocyclic and heterocyclic systems, in most cases with high regio- and stereoselectivity. In this review, an insight into the most relevant advances on sustainable Diels-Alder reactions since 2010 is provided. Various environmentally benign solvent systems are discussed, namely bio-based derived solvents (such as glycerol and gluconic acid), polyethylene glycol, deep eutectic solvents, supercritical carbon dioxide, water and water-based aqueous systems. Issues such as method's scope, efficiency, selectivity and reaction mechanism, as well as sustainability, advantages and limitations of these reaction media, are addressed.

Preparation and characterization of starch-cellulose interpenetrating network hydrogels based on sequential Diels-Alder click reaction and photopolymerization

Herein, starch-cellulose interpenetrating network (IPN) hydrogels were fabricated by sequential Diels-Alder click reaction and photopolymerization in water. Moreover, β-cyclodextrin, a commonly used host molecule in supramolecular chemistry, was also introduced to improve the performance of the IPN hydrogel. Firstly, the starch-based dienes were synthesized by modifying starch with N-maleoyl-β-alanine, and the cellulose-based dienophiles were obtained by the reaction of cellulose and furfurylamide succinate; Secondly, the as-synthesized starch-based dienes, cellulose-based dienophiles, polymerizable β-cyclodextrin, crosslinker, and acrylamide were dissolved in water and obtained a transparent solution. The solution was maintained in a water bath of 50 °C for 3 h, forming the first network via catalyst-free click Diels-Alder reaction, subsequently, the second network was formed by photopolymerization. Their preparation conditions were optimized via one-factor experiments and their properties and structures were characterized. Finally, 5- fluorouracil (5-Fu) was used as a model drug to study the sustained release behavior of the drug-loaded hydrogels. Release profile was found to fit in Ritger-Peppas kinetic model and polymer relaxation and drug diffusion made a valuable contribution to drug release. Taking into account the virtues of easily controllable photopolymerization and catalyst-free Diels-Alder reaction, the strategy described here has a potential application in the preparation of IPN hydrogels.

Fabrication, Structure and Functional Characterizations of pH-Responsive Hydrogels Derived from Phytoglycogen

The pH-responsive hydrogels were obtained through successive carboxymethylation and phosphorylase elongatation of phytoglycogen and their structure and functional characterizations were investigated. Phytoglycogen (PG) was first carboxymethylated to obtain carboxymethyl phytoglycogen (CM-PG) with degree of substitution (DS) at 0.15, 0.25, 0.30, and 0.40, respectively. Iodine staining and X-ray diffraction analysis suggested that the linear glucan chains were successfully phosphorylase-elongated from the non-reducing ends at the CM-PG surface and assembled into the double helical segments, leading to formation of the hydrogel. The DS of CM-PG significantly influenced elongation of glucan chains. Specifically, fewer glucan chains were elongated for CM-PG with higher DS and the final glucan chains were shorter, resulting in lower gelation rate of chain-elongated CM-PG and lower firmness of the corresponding hydrogels. Scanning electron microscope observed that the hydrogels exhibited a porous and interconnected morphology. The swelling ratio and volume of hydrogels was low at pH 3–5 and then became larger at pH 6–8 due to electrostatic repulsion resulting from deprotonated carboxymethyl groups. Particularly, the hydrogel prepared from chain-elongated CM-PG (DS = 0.25) showed the highest sensitivity to pH. These results suggested that phosphorylase-treated CM-PG formed the pH-responsive hydrogel and that the elongation degree and the properties of hydrogels depended on the carboxymethylation degree. Thus, it was inferred that these hydrogels was a potential carrier system of bioactive substances for their targeted releasing in small intestine.