Cross-Linked Dependency of Boronic Acid-Conjugated Chitosan Nanoparticles by Diols for Sustained Insulin Release

Benzoxaborole-grafted high molecular weight chitosan from prawn: Synthesis, characterization, target recognition and antibacterial properties

Boronated polymers are in the focus of dynamic functional materials due to the versatility of the B-O interactions and accessibility of precursors. Polysaccharides are highly biocompatible, and therefore, an attractive platform for anchoring boronic acid groups for further bioconjugation of cis-diol containing molecules. We report for the first time the introduction of benzoxaborole by amidation of the amino groups of chitosan improving solubility and introducing cis-diol recognition at physiological pH. The chemical structures and physical properties of the novel chitosan-benzoxaborole (CS-Bx) as well as two phenylboronic derivatives synthesized for comparison, were characterized by nuclear magnetic resonance (NMR), infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), dynamic light scattering (DLS), rheology and optical spectroscopic methods. The novel benzoxaborole grafted chitosan was perfectly solubilized in an aqueous buffer at physiological pH, extending the possibilities of boronated materials derived from polysaccharides. The dynamic covalent interaction between boronated chitosan and model affinity ligands, was studied by means of spectroscopy methods. A glycopolymer derived from poly(isobutylene-alt-anhydride) was also synthesized to study the formation of dynamic assemblies with benzoxaborole-grafted chitosan. A first approximation to apply fluorescence microscale thermophoresis for the interactions of the modified polysaccharide is also discussed. Additionally, the activity of CSBx against bacterial adhesion was studied.

Eco-friendly chitosan-based nanostructures in diabetes mellitus therapy: Promising bioplatforms with versatile therapeutic perspectives

Nature-derived polymers, or biopolymers, are among the most employed materials for the development of nanocarriers. Chitosan (CS) is derived from the acetylation of chitin, and this biopolymer displays features such as biocompatibility, biodegradability, low toxicity, and ease of modification. CS-based nano-scale delivery systems have been demonstrated to be promising carriers for drug and gene delivery, and they can provide site-specific delivery of cargo. Owing to the high biocompatibility of CS-based nanocarriers, they can be used in the future in clinical trials. On the other hand, diabetes mellitus (DM) is a chronic disease that can develop due to a lack of insulin secretion or insulin sensitivity. Recently, CS-based nanocarriers have been extensively applied for DM therapy. Oral delivery of insulin is the most common use of CS nanoparticles in DM therapy, and they improve the pharmacological bioavailability of insulin. Moreover, CS-based nanostructures with mucoadhesive features can improve oral bioavailability of insulin. CS-based hydrogels have been developed for the sustained release of drugs and the treatment of DM complications such as wound healing. Furthermore, CS-based nanoparticles can mediate delivery of phytochemicals and other therapeutic agents in DM therapy, and they are promising compounds for the treatment of DM complications, including nephropathy, neuropathy, and cardiovascular diseases, among others. The surface modification of nanostructures with CS can improve their properties in terms of drug delivery and release, biocompatibility, and others, causing high attention to these nanocarriers in DM therapy.

Surface engineering of chitosan nanosystems and the impact of functionalized groups on the permeability of model drug across intestinal tissue

Surface attributes of nanocarriers are crucial to determine their fate in the gastrointestinal (GI) tract. Herein, we have functionalized chitosan with biochemical moieties including rhamnolipid (RL), curcumin (Cur) and mannose (M). FTIR spectra of functionalized chitosan nanocarriers (FCNCs) demonstrated successful conjugation of M, Cur and RL. The functional moieties influenced the entrapment of model drug i.e., coumarin-6 (C6) in FCNCs with payload-hosting and non-leaching behavior i.e., >91 ± 2.5 % with negligible cumulative release of <2 % for 5 h in KREB, which was further verified in the simulated gastric and intestinal fluids. Consequently, substantial difference in the size and zeta potential was observed for FCNCs with different biochemical moieties. Scanning electron microscopy and atomic force microscopy of FCNCs displayed well-dispersed and spherical morphology. In addition, in vitro cytotoxicity results of FCNCs confirmed their hemocompatibility. In the ex-vivo rat intestinal models, FCNCs displayed a time-dependent-phenomenon in cellular-uptake and adherence. However, apparent-permeability-coefficient and flux values were in the order of C6-RL-FCNCs > C6-M-FCNCs > C6-Cur-FCNCs = C6-CNCs > Free-C6. Furthermore, the transepithelial electrical resistance revealed the FCNCs mediated recovery of membrane-integrity with reversible tight junctions opening. Thus, FCNCs have the potential to overcome the poor solubility and/or permeability issues of active pharmaceutical ingredients and transform the impact of functionalized-nanomedicines in the biomedical industry.

Antibacterial and antibiofilm activity of mannose-modified chitosan/PMLA nanoparticles against multidrug-resistant Helicobacter pylori

Because of the apparent stasis in antibiotic discoveries and the growth of multidrug resistance, Helicobacter pylori-associated gastric infections are difficult to eradicate. In the search for alternative therapy, the reductive amination of chitosan with mannose, followed by ionic gelation, produced mannose functionalized chitosan nanoparticles. Then, molecular docking and molecular dynamics (MD) simulations were conducted with H. pylori lectin (HPLectin) as a target protein involved in bacterium adherence to host cells, biofilm formation, and cytotoxicity. Changes in zeta potential and FTIR spectroscopy revealed that chitosan was functionalized with mannose. Time-kill, polystyrene adherence, and antibiofilm studies were utilized to assess nanoparticles as an alternative antibacterial treatment against a resistant gastric pathogen. Man-CS-Nps were discovered to have effective anti-adherence and biofilm disruption characteristics in suppressing the development of resistant H. pylori. In addition, bioimaging studies with CLSM, TEM, and SEM illustrated that Man-CS-Nps interacted with bacterial cells and induced membrane disruption by creating holes in the outer membranes of the bacterial cells, resulting in the leakage of amino acids. Importantly, molecular docking and 20 ns MD simulations revealed that Man-CS-Nps inhibited the target protein through slow-binding inhibition and hydrogen bond interactions with active site residues. As a consequence of the findings of this study, the Man-CS-Nps is an excellent candidate for developing alternative therapies for the increasing incidences of resistant gastric infections.

Recent Applications of Dual-Stimuli Responsive Chitosan Hydrogel Nanocomposites as Drug Delivery Tools

Polysaccharides are a versatile class of macromolecules that are involved in many biological interactions critical to life. They can be further modified for added functionality. Once derivatized, these polymers can exhibit new chemical properties that can be further optimized for applications in drug delivery, wound healing, sensor development and others. Chitosan, derived from the N-deacetylation of chitin, is one example of a polysaccharide that has been functionalized and used as a major component of polysaccharide biomaterials. In this brief review, we focus on one aspect of chitosan’s utility, namely we discuss recent advances in dual-responsive chitosan hydrogel nanomaterials.

Boronic acid sensors with double recognition sites: a review

Boronic acids reversibly and covalently bind to Lewis bases and polyols, which facilitated the development of a large number of chemical sensors to recognize carbohydrates, catecholamines, ions, hydrogen peroxide, and so on. However, as the binding mechanism of boronic acids and analytes is not very clear, it is still a challenge to discover sensors with high affinity and selectivity. In this review, boronic acid sensors with two recognition sites, including diboronic acid sensors, and monoboronic acid sensors having another group or binding moiety, are summarized. Owing to double recognition sites working synergistically, the binding affinity and selectivity of sensors can be improved significantly. This review may help researchers to sort out the binding rules and develop ideal boronic acid-based sensors.

Bio-nanotechnological advancement of orally administered insulin nanoparticles: Comprehensive review of experimental design for physicochemical characterization

Therapeutic proteins are labile macromolecules that are prone to degradation during production, freeze-drying and storage. Recent studies showed that nanoparticles can enhance the stability and oral bioavailability of encapsulated proteins. Several conventional approaches (enzyme inhibitors, mucoadhesive polymers) and novel strategies (surface modification, ligand conjugation, flash nano-complexation, stimuli-responsive drug delivery systems) have been employed to improve the physiochemical properties of nanoparticles such as size, zeta potential, morphology, polydispersity index, drug release kinetics and cell-targeting capacity. However, clinical translation of protein-based nanoparticle is limited due to poor experimental design, protocol non-compliance and instrumentation set-up that do not reflect the physiological conditions, resulting in difficulties in mass production of nanoparticles and waste in research funding. In order to address the above concerns, we conducted a comprehensive review to examine the experimental designs and conditions for physical characterization of protein-based nanoparticles. Reliable and robust characterization is essential to verify the cellular interactions and therapeutic potential of protein-based nanoparticles. Importantly, there are a number of crucial factors, which include sample treatment, analytical method, dispersants, sampling grid, staining, quantification parameters, temperature, drug concentration and research materials, should be taken into careful consideration. Variations in research protocol and unreasonable conditions that are used in optimization of pharmaceutical formulations can have great impact in result interpretation. Last but not least, we reviewed all novel instrumentations and assays that are available to examine mucus diffusion capacity, stability and bioactivity of protein-based nanoparticles. These include circular dichroism, fourier transform infrared spectroscopy, X-ray diffractogram, UV spectroscopy, differential scanning calorimetry, fluorescence spectrum, Förster resonance energy transfer, NMR spectroscopy, Raman spectroscopy, cellular assays and animal models.

Enhanced uptake of plasmid at boronic acid decorated linear polyethylenimines results in higher transfection efficiency

High molecular weight polyethylenimines (PEIs) are considered as gold standard for transfection studies; however, cytotoxicity associated with branched ones and lower charge density on linear PEIs as well as lower uptake of the resulting deoxyribonucleic acid (DNA) complexes have limited their applications in clinical studies. In order to address these concerns and improve the uptake efficiency of the DNA complexes of linear polyethylenimine (25 kDa), the polymer was grafted with variable amounts of butylboronic acid to obtain a small series of linear polyethylenimine-butylboronic acid polymers. These modified polymers were allowed to interact with plasmid DNA and the resulting complexes were characterized by physicochemical techniques. Dynamic light scattering data showed the formation of nanosized complexes with positive zeta potential values. Furthermore, when these complexes were evaluated in vitro, they not only showed enhanced cell viability but also exhibited higher transfection efficiency as compared to native linear and branched PEIs and a commercially available standard transfection reagent, Lipofectamine 2000.

Recent development of boronic acid-based fluorescent sensors

As Lewis acids, boronic acids can bind with 1,2- or 1,3-diols in aqueous solution reversibly and covalently to form five or six cyclic esters, thus resulting in significant fluorescence changes. Based on this phenomenon, boronic acid compounds have been well developed as sensors to recognize carbohydrates or other substances. Several reviews in this area have been reported before, however, novel boronic acid-based fluorescent sensors have emerged in large numbers in recent years. This paper reviews new boron-based sensors from the last five years that can detect carbohydrates such as glucose, ribose and sialyl Lewis A/X, and other substances including catecholamines, reactive oxygen species, and ionic compounds. And emerging electrochemically related fluorescent sensors and functionalized boronic acid as new materials including nanoparticles, smart polymer gels, and quantum dots were also involved. By summarizing and discussing these newly developed sensors, we expect new inspiration in the design of boronic acid-based fluorescent sensors.

As Lewis acids, boronic acids can bind with 1,2- or 1,3-diols in aqueous solution reversibly and covalently to form five or six cyclic esters, thus resulting in significant fluorescence changes.