Design of interpenetrating chitosan and poly(ethylene glycol) sponges for potential drug delivery applications

Advances in chitosan-based blends as potential drug delivery systems: A review

During the last decades, the ever-increasing incidence of diseases has led to high rates of mortality throughout the world. On the other hand, the inability and deficiencies of conventional approaches (such as chemotherapy) in the suppression of diseases remain challenging issues. As a result, there is a fundamental requirement to develop novel, biocompatible, bioavailable, and practical nanomaterials to prevent the incidence and mortality of diseases. Chitosan (CS) derivatives and their blends are outstandingly employed as promising drug delivery systems for disease therapy. These biopolymers are indicated more efficient performance against diseases compared with conventional modalities. The CS blends possess improved physicochemical properties, ease of preparation, high affordability, etc. characteristics compared with other biopolymers and even pure CS which result in efficient thermal, mechanical, biochemical, and biomedical features. Also, these blends can be administrated through different routes without a long-term treatment period. Due to the mentioned properties, numerous formulations of CS blends are developed for pharmaceutical sciences to treat diseases. This review article highlights the progressions in the development of CS-based blends as potential drug delivery systems against diseases.

Preparation and evaluation of Angelica sinensis polysaccharide-modified chitosan sponge for acute liver injury protection

In this study, a porous sponge material was formed by physically mixing chitosan (CS) and Angelica sinensis polysaccharide (ASP). After removing the water by freeze-drying, the CS/ASP sponge was obtained. The prepared sponges exhibited excellent swelling properties, thermal stability and biocompatibility as well as improvements over the insufficient mechanical properties of pure chitosan sponges. Notably, the ASP released from the CS/ASP sponge could be effectively absorbed by the liver, which endowed the CS/ASP sponge with effective liver-protective effects against CCl4-induced acute liver injury; these protective effects surpassed those of both blank CS and CS/Dextran sponges. The underlying protective mechanism may involve the activation of the Nrf2-mediated antioxidant signaling pathway and the inhibition of hepatocyte apoptosis. Understanding CS/ASP sponges may provide new insights and inspire new methods for the clinical application of ASP. At the same time, we hope to suggest future directions for the development of polysaccharide preparations.

Copolymerization Involving Sulfur-Containing Monomers

Incorporating sulfur (S) atoms into polymer main chains endows these materials with many attractive features, including a high refractive index, mechanical properties, electrochemical properties, and adhesive ability to heavy metal ions. The copolymerization involving S-containing monomers constitutes a facile method for effectively constructing S-containing polymers with diverse structures, readily tunable sequences, and topological structures. In this review, we describe the recent advances in the synthesis of S-containing polymers via copolymerization or multicomponent polymerization techniques concerning a variety of S-containing monomers, such as dithiols, carbon disulfide, carbonyl sulfide, cyclic thioanhydrides, episulfides and elemental sulfur (S8). Particularly, significant focus is paid to precise control of the main-chain sequence, stereochemistry, and topological structure for achieving high-value applications.

Chitosan-Based Polymer Blends for Drug Delivery Systems

Polymers have been widely used for the development of drug delivery systems accommodating the regulated release of therapeutic agents in consistent doses over a long period, cyclic dosing, and the adjustable release of both hydrophobic and hydrophilic drugs. Nowadays, polymer blends are increasingly employed in drug development as they generate more promising results when compared to those of homopolymers. This review article describes the recent research efforts focusing on the utilization of chitosan blends with other polymers in an attempt to enhance the properties of chitosan. Furthermore, the various applications of chitosan blends in drug delivery are thoroughly discussed herein. The literature from the past ten years was collected using various search engines such as ScienceDirect, J-Gate, Google Scholar, PubMed, and research data were compiled according to the various novel carrier systems. Nanocarriers made from chitosan and chitosan derivatives have a positive surface charge, which allows for control of the rate, duration, and location of drug release in the body, and can increase the safety and efficacy of the delivery system. Recently developed nanocarriers using chitosan blends have been shown to be cost-effective, more efficacious, and prolonged release carriers that can be incorporated into suitable dosage forms.

Chitosan-based hemostatic sponges as new generation hemostatic materials for uncontrolled bleeding emergency: Modification, composition, and applications

The choice of hemostatic technique is a curial concern for surgery and as first-aid treatment in combat. To treat uncontrolled bleeding in complex wound environments, chitosan-based hemostatic sponges have attracted significant attention in recent years because of the excellent biocompatibility, degradability, hemostasis and antibacterial properties of chitosan and their unique sponge-like morphology for high fluid absorption rate and priority aggregation of blood cells/platelets to achieve rapid hemostasis. In this review, we provide a historical perspective on the use of chitosan hemostatic sponges as the new generation of hemostatic materials for uncontrolled bleeding emergencies in complex wounds. We summarize the modification of chitosan, review the current status of preparation protocols of chitosan sponges based on various composite systems, and highlight the recent achievements on the detailed breakdown of the existing chitosan sponges to present the relationship between their composition, physical properties, and hemostatic capacity. Finally, the future opportunities and challenges of chitosan hemostatic sponges are also proposed.

Click Nucleophilic Conjugate Additions to Activated Alkynes: Exploring Thiol-yne, Amino-yne, and Hydroxyl-yne Reactions from (Bio)Organic to Polymer Chemistry

The 1,4-conjugate addition reaction between activated alkynes or acetylenic Michael acceptors and nucleophiles (i.e., the nucleophilic Michael reaction) is a historically useful organic transformation. Despite its general utility, the efficiency and outcomes can vary widely and are often closely dependent upon specific reaction conditions. Nevertheless, with improvements in reaction design, including catalyst development and an expansion of the substrate scope to feature more electrophilic alkynes, many examples now present with features that are congruent with Click chemistry. Although several nucleophilic species can participate in these conjugate additions, ubiquitous nucleophiles such as thiols, amines, and alcohols are commonly employed and, consequently, among the most well developed. For many years, these conjugate additions were largely relegated to organic chemistry, but in the last few decades their use has expanded into other spheres such as bioorganic chemistry and polymer chemistry. Within these fields, they have been particularly useful for bioconjugation reactions and step-growth polymerizations, respectively, due to their excellent efficiency, orthogonality, and ambient reactivity. The reaction is expected to feature in increasingly divergent application settings as it continues to emerge as a Click reaction.

Tunable and high tissue adhesive properties of injectable chitosan based hydrogels through polymer architecture modulation

Chitosan-based hydrogels have been widely used for various biomedical applications due to their versatile properties such as biocompatibility, biodegradability, muco-adhesiveness, hemostatic effect and so on. However, the inherent rigidity and brittleness of pure chitosan hydrogels are still unmanageable, which has limited their potential use in biomaterial research. In this study, we developed in situ forming chitosan/PEG hydrogels with improved mechanical properties, using the enzymatic crosslinking reaction of horseradish peroxidase (HRP). The effect of PEG on physico-chemical properties of hybrid hydrogels was thoroughly elucidated by varying the content (0-100 %), molecular weight (4, 10 and 20 kDa) and geometry (linear, 4-arm) of the PEG derivatives. The resulting hydrogels demonstrated excellent hemostatic ability and are highly biocompatible in vivo, comparable to commercially available fibrin glue. We suggest these chitosan/PEG hybrid hydrogels with tunable physicochemical and tissue adhesive properties have great potential for a wide range of biomedical applications in the near future.

Burgeoning Polymer Nano Blends for Improved Controlled Drug Release: A Review

With continual rapid developments in the biomedical field and understanding of the important mechanisms and pharmacokinetics of biological molecules, controlled drug delivery systems (CDDSs) have been at the forefront over conventional drug delivery systems. Over the past several years, scientists have placed boundless energy and time into exploiting a wide variety of excipients, particularly diverse polymers, both natural and synthetic. More recently, the development of nano polymer blends has achieved noteworthy attention due to their amazing properties, such as biocompatibility, biodegradability and more importantly, their pivotal role in controlled and sustained drug release in vitro and in vivo. These compounds come with a number of effective benefits for improving problems of targeted or controlled drug and gene delivery systems; thus, they have been extensively used in medical and pharmaceutical applications. Additionally, they are quite attractive for wound dressings, textiles, tissue engineering, and biomedical prostheses. In this sense, some important and workable natural polymers (namely, chitosan (CS), starch and cellulose) and some applicable synthetic ones (such as poly-lactic-co-glycolic acid (PLGA), poly(lactic acid) (PLA) and poly-glycolic acid (PGA)) have played an indispensable role over the last two decades for their therapeutic effects owing to their appealing and renewable biological properties. According to our data, this is the first review article highlighting CDDSs composed of diverse natural and synthetic nano biopolymers, blended for biological purposes, mostly over the past five years; other reviews have just briefly mentioned the use of such blended polymers. We, additionally, try to make comparisons between various nano blending systems in terms of improved sustained and controlled drug release behavior.

Chemical Synthesis and Characterization of Poly(poly(ethylene glycol) methacrylate)-Grafted CdTe Nanocrystals via RAFT Polymerization for Covalent Immobilization of Adenosine

This paper describes the functionalization of poly(poly(ethylene glycol) methacrylate) (PPEGMA)-grafted CdTe (PPEGMA-g-CdTe) quantum dots (QDs) via surface-initiated reversible addition–fragmentation chain transfer (SI-RAFT) polymerization for immobilization of adenosine. Initially, the hydroxyl-coated CdTe QDs, synthesized using 2-mercaptoethanol (ME) as a capping agent, were coupled with a RAFT agent, S-benzyl S′-trimethoxysilylpropyltrithiocarbonate (BTPT), through a condensation reaction. Then, 2,2′-azobisisobutyronitrile (AIBN) was used to successfully initiate in situ RAFT polymerization to generate PPEGMA-g-CdTe nanocomposites. Adenosine-above-PPEGMA-grafted CdTe (Ado-i-PPEGMA-g-CdTe) hybrids were formed by the polymer shell, which had successfully undergone bioconjugation and postfunctionalization by adenosine (as a nucleoside). Fourier transform infrared (FT-IR) spectrophotometry, energy-dispersive X-ray (EDX) spectroscopy, thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy results indicated that a robust covalent bond was created between the organic PPEGMA part, cadmium telluride (CdTe) QDs, and the adenosine conjugate. The optical properties of the PPEGMA-g-CdTe and Ado-i-PPEGMA-g-CdTe hybrids were investigated by photoluminescence (PL) spectroscopy, and the results suggest that they have a great potential for application as optimal materials in biomedicine.