Characterization of a water-soluble chitosan derivative and its potential for submucosal injection in endoscopic techniques

Enhancing oral delivery and anticancer efficacy of 7-ethyl-10-hydroxycamptothecin through self-assembled micelles of deoxycholic acid grafted N'-nonyl-trimethyl chitosan

Irinotecan (CPT-11) is used as a first or second-line chemotherapy drug for the treatment and management of colorectal cancers. In vitro studies have shown that 7-ethyl-10-hydroxycamptothecin (SN38), the active metabolite of CPT-11, displays promising anticancer efficacy. However, its poor aqueous solubility and hydrolytic degradation result in its lower oral bioavailability and impracticable clinical application. To overcome these limitations, a novel amphiphilic chitosan derivative, deoxycholic acid decorated N'-nonyl-trimethyl chitosan, was synthesized. Nano-micelles loaded with SN38 were subsequently prepared to enhance the bioavailability and anti-tumor efficacy of the drug through oral administration. The nano-micelles demonstrated improved dilution stability, enhanced greater mucosal adherence, significant P-gp efflux inhibition, and increased drug transport in the intestine by paracellular and transcellular pathways. Consequently, both the in vivo pharmacokinetic profile and therapeutic efficacy of SN38 against cancer were substantially improved via the micellar system. Thus, the developed polymeric micelles can potentially enhance the SN38 oral absorption for cancer therapy, offering prospective avenues for further exploration.

Current application and modification strategy of marine polysaccharides in tissue regeneration: A review

Marine polysaccharides (MPs) are exceptional bioactive materials that possess unique biochemical mechanisms and pharmacological stability, making them ideal for various tissue engineering applications. Certain MPs, including agarose, alginate, carrageenan, chitosan, and glucan have been successfully employed as biological scaffolds in animal studies. As carriers of signaling molecules, scaffolds can enhance the adhesion, growth, and differentiation of somatic cells, thereby significantly improving the tissue regeneration process. However, the biological benefits of pure MPs composite scaffold are limited. Therefore, physical, chemical, enzyme modification and other methods are employed to expand its efficacy. Chemically, the structural properties of MPs scaffolds can be altered through modifications to functional groups or molecular weight reduction, thereby enhancing their biological activities. Physically, MPs hydrogels and sponges emulate the natural extracellular matrix, creating a more conducive environment for tissue repair. The porosity and high permeability of MPs membranes and nanomaterials expedite wound healing. This review explores the distinctive properties and applications of select MPs in tissue regeneration, highlighting their structural versatility and biological applicability. Additionally, we provide a brief overview of common modification strategies employed for MP scaffolds. In conclusion, MPs have significant potential and are expected to be a novel regenerative material for tissue engineering.

Multifunctional two-component in-situ hydrogel for esophageal submucosal dissection for mucosa uplift, postoperative wound closure and rapid healing

Endoscopic submucosal dissection (ESD) for gastrointestinal tumors and premalignant lesions needs submucosal fluid cushion (SFC) for mucosal uplift before dissection, and wound care including wound closure and rapid healing postoperatively. Current SFC materials as well as materials and/or methods for post-ESD wound care have single treatment effect and hold corresponding drawbacks, such as easy dispersion, short duration, weak hemostasis and insufficient repair function. Thus, designing materials that can serve as both SFC materials and wound care is highly desired, and remains a challenge. Herein, we report a two-component in-situ hydrogel prepared from maleimide-based oxidized sodium alginate and sulfhydryl carboxymethyl-chitosan, which gelated mainly based on "click" chemistry and Schiff base reaction. The hydrogels showed short gelation time, outstanding tissue adhesion, favorable hemostatic properties, and good biocompatibility. A rat subcutaneous ultrasound model confirmed the ability of suitable mucosal uplift height and durable maintenance time of AM solution. The in vivo/in vitro rabbit liver hemorrhage model demonstrated the effects of hydrogel in rapid hemostasis and prevention of delayed bleeding. The canine esophageal ESD model corroborated that the in-situ hydrogel provided good mucosal uplift and wound closure effects, and significantly accelerated wound healing with accelerating re-epithelization and ECM remodeling post-ESD. The two-component in-situ hydrogels exhibited great potential in gastrointestinal tract ESD.

Hydrogels for Mucosal Drug Delivery

Mucosal tissues are often a desirable site of drug action to treat disease and engage the immune system. However, systemically administered drugs suffer from limited bioavailability in mucosal tissues where technologies to enable direct, local delivery to these sites would prove useful. In this Spotlight on Applications article, we discuss hydrogels as an attractive means for local delivery of therapeutics to address a range of conditions affecting the eye, nose, oral cavity, gastrointestinal, urinary bladder, and vaginal tracts. Considering the barriers to effective mucosal delivery, we provide an overview of the key parameters in the use of hydrogels for these applications. Finally, we highlight recent work demonstrating their use for inflammatory and infectious diseases affecting these tissues.

Design and validation of performance-oriented injectable chitosan thermosensitive hydrogels for endoscopic submucosal dissection

Endoscopic submucosal dissection (ESD) is a challenging procedure. The use of biomaterials to improve the operator's convenience (operating affinity) has received little attention. We prepared two thermosensitive hydrogels, lactobionic acid-modified chitosan/chitosan/β-glycerophosphate thermosensitive hydrogel (hydrogel 1) and its lyophilized powders (hydrogel 2), characterized their physicochemical properties and evaluated their performance in ESD experiments on large animals, by comparing with the commonly used normal saline (NS) and glycerin fructose (GF). These hydrogels showed good low-temperature fluidity; their viscosities at 4 °C were 92.2 mPa.s and 26.9 mPa.s, respectively. The hydrogels provided significantly better viscoelastic properties than NS and GF. The relaxation moduli of hydrogels were higher than those of NS and GF when the strains were 1 %, 5 %, and 10 %. The hydrogels can be maintained for seven days, even at pH 1, after which they degrade entirely. In pig model experiments, we performed submucosal injection and ESD procedures in the stomach and esophagus. The cushion height produced by the hydrogels was higher than those of NS and GF 30 min after injection. The ESD operation time for hydrogels was significantly shorter. Postoperative wound observation and histological analysis showed that the hydrogels promoted wound healing. The two hydrogels differed in fluidity, viscoelasticity, and other properties, which makes it possible to select the hydrogels according to the size and location of the lesion during ESD operation, and hydrogel 2 may be more suitable for use in lengthier procedures. In general, the hydrogels showed good performance, facilitated the intraoperative operation of ESD, shorten the operation time and promoted wound healing, which is of great significance for reducing the complications and reducing the threshold of ESD operation and further promoting the popularity of ESD.

Preparation and ex vivo investigation of an injectable microparticulate formulation for gastrointestinal mucosa polyp resection

Endoscopic submucosal dissection (ESD) and endoscopic submucosal resection (EMR) are non-invasive endoscopic techniques. They allow an early excised gastrointestinal (GI) mucosal precancerous lessions. For their application is necessary use of a submucosal injection that lift area to excise. The main objective of this study was the preparation of microparticulate-based fluid for injection in the GI submucosa. Alginate microparticles (MPs) were developed by the solvent displacement technique and characterized by particle size, surface electrical properties, swelling, degradation, rheology, adhesion and leakage, syringeablity and stability. Furthermore, their potential to form a submucosal cushion was assayed in porcine stomach mucosa and porcine colon mucosa. Results showed MPs sizes below 160 μm, negative surface charge around -50 mV at pH=6, high rates of swelling and good adhesion. The microparticulate-based fluid exhibited pseudoplastic behavior following the Ostwald-de Waele rheological model. A brief force is sufficient for its injection through a syringe. Finally, formulations were able to provide a submucosa elevation of 1.70 cm for more than 90 min and 120 min in the porcine stomach and colon, respectively.

Chitosan thermosensitive hydrogels based on lyophilizate powders demonstrate significant potential for clinical use in endoscopic submucosal dissection procedures

The goal of this study was to develop intraoperative biomaterials for use in endoscopic submucosal dissection (ESD) procedures that are stable during storage, easy to use, and effective in clinical practice. Therefore, injectable thermosensitive hydrogels were developed based on lactobionic acid-modified chitosan/chitosan/β-glycerophosphate (CSLA/CS/GP) hydrogel lyophilizate powders, and their properties were compared with original hydrogels that had not been freeze-dried. The results indicated that the lyophilizate powders retained their thermosensitive properties, and gels could be formed within 5 min at 37 °C. Compared to the original hydrogels, the injectability of the hydrogels derived from lyophilizate powders increased significantly. These novel materials maintained their original porous network lamellar structure but exhibited improved mechanical strength and tissue adhesion. Their application with L929 and GES-1 cells revealed that the lyophilizate powder hydrogels demonstrated good cytocompatibility and clearly protected the cells in an acidic environment. The results of submucosal injection experiments involving porcine stomach tissue indicated that the heights of the cushions created by CSLA/CS/GP lyophilizate powder hydrogels lasted longer than those generated with normal saline. The thermosensitive hydrogels based on lyophilizate powders may contribute to practical clinical applications involving ESD, and may also have potential value for other applications in the digestive tract.

Oxidative stress and cyto-genotoxicity induced by poly-d-glucosamine in human blood cells in vitro

Poly-N-acetyl-d-glucosamine (CH; chitin) is the main component of the insect skeleton, fungal cell wall, and many crustaceans, including crab and shrimp. CH is the most abundant in nature after cellulose, and it has a complex and hardly soluble structure. Poly-d-glucosamine (CHO; chitosan) is a soluble derivative of CH produced by deacetylation used in many fields, including human health. This study carried out the cytotoxic, genotoxic, and oxidative effects of CHO on human whole blood (hWB) and lymphocytes (LYMs) in dose ranges 6.25-2000 μg/mL, in vitro. Total antioxidant capacity (TAC) and total oxidant status (TOS) analyzes were performed on plasma to appreciate oxidative stress. 3-(4,5-Dimethylthiazol-2-yl)-2,5 diphenyltetrazolium bromide (MTT) and lactate dehydrogenase (LDH) assays were applied to understand the cytotoxicity. Chromosomal aberration (CA) and micronucleus (MN) methods were practiced to evaluate genotoxicity. 6.25-150 μg/mL doses increased TAC and decreased TOS. A decreasing and increasing curve from 200 to 2000 μg/mL on TAC and TOS values were determined, respectively. 0-250 μg/mL doses did not provide any cytotoxic data. However, 500-2000 μg/mL doses showed increasing cytotoxicity and genotoxicity. The study results showed that CHO does not pose a toxic risk to human health at low doses but may pose a threat at high doses.

Viscosity and degradation controlled injectable hydrogel for esophageal endoscopic submucosal dissection

Endoscopic submucosal dissection (ESD) is a common procedure to treat early and precancerous gastrointestinal lesions. Via submucosal injection, a liquid cushion is created to lift and separate the lesion and malignant part from the muscular layer where the formed indispensable space is convenient for endoscopic incision. Saline is a most common submucosal injection liquid, but the formed liquid pad lasts only a short time, and thus repeated injections increase the potential risk of adverse events. Hydrogels with high osmotic pressure and high viscosity are used as an alternate; however, with some drawbacks such as tissue damage, excessive injection resistance, and high cost. Here, we reported a nature derived hydrogel of gelatin-oxidized alginate (G-OALG). Based on the rheological analysis and compare to commercial endoscopic mucosal resection (EMR) solution (0.25% hyaluronic acid, HA), a designed G-OALG hydrogel of desired concentration and composition showed higher performances in controllable gelation and injectability, higher viscosity and more stable structures. The G-OALG gel also showed lower propulsion resistance than 0.25% HA in the injection force assessment under standard endoscopic instruments, which eased the surgical operation. In addition, the G-OALG hydrogel showed good in vivo degradability biocompatibility. By comparing the results acquired via ESD to normal saline, the G-OALG shows great histocompatibility and excellent endoscopic injectability, and enables create a longer-lasting submucosal cushion. All the features have been confirmed in the living both pig and rat models. The G-OALG could be a promising submucosal injection agent for esophageal ESD.

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Injectable gel with controlled viscosity.

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Injectable gel with controlled degradation.

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Making esophageal submucosal liquid cushion.

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Potential treatment for early esophageal cancer.

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Big animal in-situ imaging.

Natural-based Hydrogels: A Journey from Simple to Smart Networks for Medical Examination

Natural hydrogels, due to their unique biological properties, have been used extensively for various medical and clinical examinations that are performed to investigate the signs of disease. Recently, complex-crosslinking strategies improved the mechanical properties and advanced approaches have resulted in the introduction of naturally derived hydrogels that exhibit high biocompatibility, with shape memory and self-healing characteristics. Moreover, the creation of self-assembled natural hydrogels under physiological conditions has provided the opportunity to engineer fine-tuning properties. To highlight recent studies of natural-based hydrogels and their applications for medical investigation, a critical review was undertaken using published papers from the Science Direct database. This review presents different natural-based hydrogels (natural, natural-synthetic hybrid and complex-crosslinked hydrogels), their historical evolution, and recent studies of medical examination applications. The application of natural-based hydrogels in the design and fabrication of biosensors, catheters and medical electrodes, detection of cancer, targeted delivery of imaging compounds (bioimaging) and fabrication of fluorescent bioprobes is summarised here. Without doubt, in future, more useful and practical concepts will be derived to identify natural-based hydrogels for a wide range of clinical examination applications.

Interaction Between Chitosan and Mucin: Fundamentals and Applications

The term chitosan (CS) refers to a family of aminopolysaccharides derived from chitin. Among other properties, CS is nontoxic, mucoadhesive and can be used for load and transport drugs. Given these and other physicochemical and biological properties, CS is an optimal biopolymer for the development of transmucosal drug delivery systems, as well as for the treatment of pathologies related to mucosal dysfunctions. Mucins are glycoprotein macromolecules that are the major components of mucus overlaying epithelia. CS interacts with mucin and adsorbs on and changes the rheology of mucus. However, CS and mucins denote families of polymers/macromolecules with highly variable chemical structure, properties, and behavior. To date, their interactions at the molecular level have not been completely unraveled. Also, the properties of complexes composed of CS and mucin vary as a function of the sources and preparation of the polymers. As a consequence, the mucoadhesion and drug delivery properties of such complexes vary as well. The breadth of this review is on the molecular interactions between CS and mucin. In particular, in vitro and ex vivo characterization methods to investigate both the interactions at play during the formation of CS-mucin complexes, and the advances on the use of CS for transmucosal drug delivery are addressed.

Development of Mucoadhesive Chitosan Derivatives for Use as Submucosal Injections

Endoscopic mucosal resection (EMR) and endoscopic submucosal dissection (ESD) have been used for surgical treatment of early gastric cancer. These endoscopic techniques require proper submucosal injections beneath the tumor to provide a sufficiently high submucosal fluid cushion (SFC) to facilitate clean dissection and resection of the tumor. Until now, the submucosal injection materials developed for endoscopic techniques such as EMR and ESD of tumors have been composed of macromolecules, proteins, or polysaccharides. We have been investigating the use of chitosan, a product that is obtained by the alkaline deacetylation of chitin, the second-most abundant natural polysaccharide. Specifically, we have been studying a photocrosslinked chitosan hydrogel (PCH) and solubilized chitosan derivatives for use as novel submucosal injections for endoscopic techniques. Notably, chitosan derivatives with lactose moieties linked to the amino groups of its glucosamine units can specifically interact with acidic mucopolysaccharides and mucins in submucosa without the need for the incorporation of harmful photoreactive groups nor potentially mutagenic ultraviolet irradiation.