Liquid-liquid and liquid-solid separation in self-assembled chitosan-alginate and chitosan-pectin complexes

The complexation between two oppositely charged polyelectrolytes (PE) can lead liquid-liquid (complex coacervates, CC) or liquid-solid (solid precipitates, SP) phase separations. Herein, the effect of pH (2-11) and ionic strength (I, 0.05-1.0 M KCl) on the associative interactions between chitosan (QL)-alginate (SA) and QL-Pectin (Pec), polysaccharides widely used in biotechnology field, is described. pH and I, exhibited significant effect on the structure and phase transitions by modifying the ionization degree (α), pk_a, and associative interactions between PE. Onset of binding was established at pH_c 9, while continued acidification (pH_τ 5.8) led to simultaneous CC and SP exhibiting a maximum turbidity in both systems. At pH_δ 4.0, QL-Pec showed preferably CC structures whereas QL-SA maintained the CC and SP structures. At pH_ω 2, the associative interactions were suppressed due to the low ionization of Pec and SA. I (1.0 M) significantly diminished the interactions in QL-Pec due to charge screening. Molecular weight, second virial coefficient, hydrodynamic size, ionizable groups, and persistence length of polyion, influenced on the phase behavior of QL-Pec and QL-SA systems. Therefore, CC and SP are found simultaneously in both systems, their transitions can be modulated by intrinsic and environmental conditions, expanding the functional properties of complexed polysaccharides.

Mucoadhesive Marine Polysaccharides

Mucoadhesive polymers are of growing interest in the field of drug delivery due to their ability to interact with the body’s mucosa and increase the effectiveness of the drug. Excellent mucoadhesive performance is typically observed for polymers possessing charged groups or non-ionic functional groups capable of forming hydrogen bonds and electrostatic interactions with mucosal surfaces. Among mucoadhesive polymers, marine carbohydrate biopolymers have been attracting attention due to their biocompatibility and biodegradability, sample functional groups, strong water absorption and favorable physiochemical properties. Despite the large number of works devoted to mucoadhesive polymers, there are very few systematic studies on the influence of structural features of marine polysaccharides on mucoadhesive interactions. The purpose of this review is to characterize the mucoadhesive properties of marine carbohydrates with a focus on chitosan, carrageenan, alginate and their use in designing drug delivery systems. A wide variety of methods which have been used to characterize mucoadhesive properties of marine polysaccharides are presented in this review. Mucoadhesive drug delivery systems based on such polysaccharides are characterized by simplicity and ease of use in the form of tablets, gels and films through oral, buccal, transbuccal and local routes of administration.

New insights into physicochemical aspects involved in the formation of polyelectrolyte complexes based on chitosan and dextran sulfate

Polyelectrolyte complexation is a technique based on interactions between polyelectrolytes of opposite charges driven by supramolecular interactions. Although many studies address the formation of polyelectrolyte complexes (PECs), few explore strategies and tools to select the best working conditions and are often based on empirical choices. This study evaluates the influence of pH, molecular weight, and polymeric proportion on the formation of PECs based on chitosan:dextran sulfate. In addition, it assesses the approaches that study the influence of pH on the zeta potential of polymeric dispersions as a tool in the design of PECs. Results showed that nanoparticles with an excess of polycation formed aggregates, while an excess of dextran sulfate reduced the size of the particles. The graph of zeta potential as a function of pH proved to be a promising tool in the choice of polymers and a better pH condition in the development of PECs.

Understanding the Effect of Conformational Rigidity on Rheological Behavior and Formation of Polysaccharide-Based Hybrid Hydrogels

The importance of conformational rigidity on macroscopic rheological properties was revealed using two model polysaccharides, namely, xanthan gum and hyaluronic acid. Xanthan gum has a rigid tertiary conformation due to its ordered double-helical structure, and the interactions between the tertiary structures result in the formation of a network/quaternary structure. In comparison, hyaluronic acid possesses a relatively flexible tertiary conformation due to its secondary random coil structure. Xanthan gum exhibits a much stronger shear thinning and more solidlike behavior compared to hyaluronic acid, owing to its network/quaternary structure. The rigid tertiary structure and the presence of a network/quaternary structure also endow xanthan gum with better resistance against environmental changes (e.g., salt and/or urea addition, temperature change) compared to hyaluronic acid. The network/quaternary structure allows xanthan gum to form gels with chitosan via electrostatic interactions when using the vapor-induced gelation technique, which is not possible for hyaluronic acid due to its flexible tertiary conformation under similar conditions.

Determination of indicators allowing to evaluating the hemostatic activity of chitosan without a biological experiment

The biopolymer chitosan is widely used for the development of local hemostatic agents. However, the physicochemical parameters of chitosan that determine its hemostatic properties have not yet been determined. Standard quality control of chitosan-containing raw materials and medical products on its basis do not allow us to make a conclusion about the effectiveness of their use for stopping bleeding. The most reliable method for assessing hemostatic activity remains in vivo experiment on large animals. The aim of this study was to determine additional physicochemical parameters of chitosan, which would make it possible to predict its hemostatic activity without conducting a biological experiment. In this work, using the methods of nuclear magnetic resonance spectroscopy, spectrophotometry and viscometry, it has been shown that the ability to initiate hemostasis is depending of the molecular weight and degree of deacetylation of chitosan, but not enough linearly. The hemostatic properties in vitro increases in a series of samples with a relatively constant molecular weight with an increase in the degree of deacetylation. As well as in a series with the same degree of deacetylation with an increase in molecular weight. However, at molecular weight values more than 300 kDa, the viscosity of the polymer causes the opposite effect: with an increase in the degree of deacetylation, the hemostatic activity decreases. The best ability to initiate hemostasis have chitosan samples with a degree of deacetylation of 90.0%–97.4% and molecular weight 145.7–284.7 kDa, in which at pH of solution close to physiological, a significant part of the molecules transitioned from conformation state rigid rod to state globule. It was accompanied by an abrupt change in light transmission of the solution. It was concluded, that it is possible to study conformational states by spectrophotometry to assess the hemostatic activity of chitosan samples without performing biological experiment.

Nose-to-brain co-delivery of drugs for glioblastoma treatment using nanostructured system

Mutations on the epidermal growth factor receptor (EGFR), induction of angiogenesis, and reprogramming cellular energetics are all biological features acquired by tumor cells during tumor development, and also known as the hallmarks of cancer. Targeted therapies that combine drugs that are capable of acting against such concepts are of great interest, since they can potentially improve the therapeutic efficacy of treatments of complex pathologies, such as glioblastoma (GBM). However, the anatomical location and biological behavior of this neoplasm imposes great challenges for targeted therapies. A novel strategy that combines alpha-cyano-4-hydroxycinnamic acid (CHC) with the monoclonal antibody cetuximab (CTX), both carried onto a nanotechnology-based delivery system, is herein proposed for GBM treatment via nose-to-brain delivery. The biological performance of Poly (D,L-lactic-co-glycolic acid)/chitosan nanoparticles (NP), loaded with CHC, and conjugated with CTX by covalent bonds (conjugated NP) were extensively investigated. The NP platforms were able to control CHC release, indicating that drug release was driven by the Weibull model. An ex vivo study with nasal porcine mucosa demonstrated the capability of these systems to promote CHC and CTX permeation. Blot analysis confirmed that CTX, covalently associated to NP, impairs EGRF activation. The chicken chorioallantoic membrane assay demonstrated a trend of tumor reduction when conjugated NP were employed. Finally, images acquired by fluorescence tomography evidenced that the developed nanoplatform was effective in enabling nose-to-brain transport upon nasal administration. In conclusion, the developed delivery system exhibited suitability as an effective novel co-delivery approaches for GBM treatment upon intranasal administration.

Computational and experimental approaches for chitosan-based nano PECs design: Insights on a deeper comprehension of nanostructure formation

Nanostructured polyelectrolyte complexes (nano PECs) based on biopolymers are an important technological strategy to target drugs to the action and/or absorption site in a more effective way. In this work, computational studies were performed to predict the ionization, spatial arrangement and interaction energies of chitosan (CS), hyaluronic acid (HA), and hypromellose phthalate (HP), for the design of nano PEC carriers for methotrexate (MTX). The optimal pH range (5.0-5.5) for preparing nano PECs was selected by experimental and computational methodologies, favoring the polymers interactions. CS, HA, HP and MTX addition order was also rationalized, maximizing their interactions and MTX entrapment. Spherical nano-sized particles (256-575 nm, by dynamic light scattering measurement) with positive surface charge (+25.5 to +29.2 mV) were successfully prepared. The MTX association efficiency ranged from 20 to 32 %. XRD analyses evidenced the formation of a new material with an organized structure, in relation to raw polymers.