Synthesis and characterization of timolol maleate-loaded quaternized chitosan-based thermosensitive hydrogel: A transparent topical ocular delivery system for the treatment of glaucoma

A review on revolutionizing ophthalmic therapy: Unveiling the potential of chitosan, hyaluronic acid, cellulose, cyclodextrin, and poloxamer in eye disease treatments

Ocular disorders, encompassing both common ailments like dry eye syndrome and more severe situations for instance age-related macular degeneration, present significant challenges to effective treatment due to the intricate architecture and physiological barriers of the eye. Polysaccharides are emerging as potential solutions for drug delivery to the eyes due to their compatibility with living organisms, natural biodegradability, and adhesive properties. In this review, we explore not only the recent advancements in polysaccharide-based technologies and their transformative potential in treating ocular illnesses, offering renewed optimism for both patients and professionals but also anatomy of the eye and the significant obstacles hindering drug transportation, followed by an investigation into various drug administration methods and their ability to overcome ocular-specific challenges. Our focus lies on biological adhesive polymers, including chitosan, hyaluronic acid, cellulose, cyclodextrin, and poloxamer, known for their adhesive characteristics enhancing drug retention on ocular surfaces and increasing bioavailability. A detailed analysis of material designs used in ophthalmic formulations, such as gels, lenses, eye drops, nanofibers, microneedles, microspheres, and nanoparticles, their advantages and limitations, the potential of formulations in improving therapeutic outcomes for various eye conditions. Moreover, we underscore the discovery of novel polysaccharides and their potential uses in ocular drug delivery.

Biomedical Trends in Stimuli-Responsive Hydrogels with Emphasis on Chitosan-Based Formulations

Biomedicine is constantly evolving to ensure a significant and positive impact on healthcare, which has resulted in innovative and distinct requisites such as hydrogels. Chitosan-based formulations stand out for their versatile utilization in drug encapsulation, transport, and controlled release, which is complemented by their biocompatibility, biodegradability, and non-immunogenic nature. Stimuli-responsive hydrogels, also known as smart hydrogels, have strictly regulated release patterns since they respond and adapt based on various external stimuli. Moreover, they can imitate the intrinsic tissues' mechanical, biological, and physicochemical properties. These characteristics allow stimuli-responsive hydrogels to provide cutting-edge, effective, and safe treatment. Constant progress in the field necessitates an up-to-date summary of current trends and breakthroughs in the biomedical application of stimuli-responsive chitosan-based hydrogels, which was the aim of this review. General data about hydrogels sensitive to ions, pH, redox potential, light, electric field, temperature, and magnetic field are recapitulated. Additionally, formulations responsive to multiple stimuli are mentioned. Focusing on chitosan-based smart hydrogels, their multifaceted utilization was thoroughly described. The vast application spectrum encompasses neurological disorders, tumors, wound healing, and dermal infections. Available data on smart chitosan hydrogels strongly support the idea that current approaches and developing novel solutions are worth improving. The present paper constitutes a valuable resource for researchers and practitioners in the currently evolving field.

Novel Biomaterials in Glaucoma Treatment

Glaucoma is a significant cause of blindness worldwide, and its treatment remains challenging. The disease progressively leads to damage to the optic disc and thus loss of visual acuity and visual field. High intraocular pressure (IOP) is a common risk factor. There are three major methods to treat this disease: topical, laser, and surgical. None of these are completely satisfactory; therefore, alternatives using new biomaterials are being sought. Since biomaterial engineering has experienced significant growth in recent decades, its products are gradually being introduced to various branches of medicine, with the exception of ophthalmology. Biomaterials, such as glaucoma drainage implants, have been successfully used to treat glaucoma. There is significant ongoing research on biomaterials as drug delivery systems that could overcome the disadvantages of topical glaucoma treatment, such as poor intraocular penetration or frequent drug administration. This article summarizes the use of novel biomaterials for glaucoma treatment presented in the literature. The literature search was based on articles published in English on PubMed.gov, Cochranelibrary.com, and Scopus.com between 2018 and 2023 using the following term "biomaterials in glaucoma." A total of 103 published articles, including twenty-two reviews, were included. Fifty-nine articles were excluded on the basis of their titles and abstracts.

Dual-functional thermosensitive hydrogel for reducing infection and enhancing bone regeneration in infected bone defects

The contamination of bone defects is a serious therapeutic problem. The treatment of infected bone defects involves rigorous infection control followed by bone reconstruction. Considering these two processes, the development of biomaterials possessing antibacterial and osteogenic properties offers a promising approach for the treatment of infected bone defects. In this study, a dual-functional, thermosensitive, and injectable hydrogel composed of chitosan (CS), quaternized CS (QCS), and nano-hydroxyapatite (nHA) was designed, and the ratio of CS to QCS in the hydrogel was optimized to enhance the antibacterial efficacy of CS while reducing the cytotoxicity of QCS. In vitro studies demonstrated that the hydrogel with an 85 %:15 % ratio of CS to QCS exhibited excellent biocompatibility and antibacterial properties while also possessing suitable mechanical characteristics and degradability. The incorporation of nHA into the hydrogel enhanced MC3T3-E1 proliferation and osteogenic differentiation. Moreover, this hydrogel demonstrated superior in vivo therapeutic effectiveness in a rabbit model of infected bone defect. In summary, this study provides a promising material design and a comprehensive one-step treatment strategy for infected bone defects.

Polysaccharides polymers for glaucoma treatment-a review

One of the major challenges in preventing glaucoma progression is patient compliance with medication regimens. Since conventional ophthalmic dosage forms have numerous limitations, researchers have been intensively working on developing polymers-based delivery systems for glaucoma drugs. Specifically, research and development efforts have increased using polysaccharide polymers such as sodium alginate, cellulose, β-cyclodextrin, hyaluronic acid, chitosan, pectin, gellan gum, galactomannans for sustained release to the eye to overcome treatment challenges, showing promise in improving drug release and delivery, patient experience, and treatment compliance. In the recent past, multiple research groups have successfully designed sustained drug delivery systems, promoting the efficacy as well as the feasibility of glaucoma drugs with single/combinations of polysaccharides to eliminate the drawbacks associated with the glaucoma treatment. Naturally available polysaccharides, when used as drug vehicles can increase the retention time of eye drops on the ocular surface, leading to improved drug absorption and bioavailability. Additionally, some polysaccharides can form gels or matrices that can release drugs slowly over time, providing sustained drug delivery and reducing the need for frequent dosing. Thus, this review aims to provide an overview of the pre-clinical and clinical studies of polysaccharide polymers applied for glaucoma treatment along with their therapeutic outcomes.

Polymer-Based Self-Assembled Drug Delivery Systems for Glaucoma Treatment: Design Strategies and Recent Advances

Glaucoma has become the world's leading cause of irreversible blindness, and one of its main characteristics is high intraocular pressure. Currently, the non-surgical drug treatment scheme to reduce intraocular pressure is a priority method for glaucoma treatment. However, the complex and special structure of the eye poses significant challenges to the treatment effect and safety adherence of this drug treatment approach. To address these challenges, the application of polymer-based self-assembled drug delivery systems in glaucoma treatment has emerged. This review focuses on the utilization of polymer-based self-assembled structures or materials as important functional and intelligent carriers for drug delivery in glaucoma treatment. Various drug delivery systems, such as eye drops, hydrogels, and contact lenses, are discussed. Additionally, the review primarily summarizes the design strategies and methods used to enhance the treatment effect and safety compliance of these polymer-based drug delivery systems. Finally, the discussion delves into the new challenges and prospects of employing polymer-based self-assembled drug delivery systems for the treatment of glaucoma.

Applications and Recent Developments of Hydrogels in Ophthalmology

Hydrogels are a type of functional polymer material with a three-dimensional network structure composed of physically or chemically cross-linked polymers. All hydrogels have two common features: first, their structure contains a large number of hydrophilic groups; therefore, they have a high water content and can swell in water. Second, they have good regulation, and the physical and chemical properties of their cross-linked network can be changed by environmental factors and deliberate modification methods. In recent years, the application of hydrogels in ophthalmology has gradually attracted attention. By selecting an appropriate composition and cross-linking mode, hydrogels can be used in different fields for various applications, such as gel eye drops, in situ gel preparation, intravitreal injection, and corneal contact lenses. This Review provides a detailed introduction to the classification of hydrogels and their applications in glaucoma, vitreous substitutes, fundus diseases, corneal contact lenses, corneal diseases, and cataract surgery.

Carboxymethyl Chitosan Microgels for Sustained Delivery of Vancomycin and Long-Lasting Antibacterial Effects

Carboxymethyl chitosan (CMCh) is a unique polysaccharide with functional groups that can develop positive and negative charges due to the abundant numbers of amine and carboxylic acid groups. CMCh is widely used in different areas due to its excellent biocompatibility, biodegradability, water solubility, and chelating ability. CMCh microgels were synthesized in a microemulsion environment using divinyl sulfone (DVS) as a crosslinking agent. CMCh microgel with tailored size and zeta potential values were obtained in a single stem by crosslinking CMCh in a water-in-oil environment. The spherical microgel structure is confirmed by SEM analysis. The sizes of CMCh microgels varied from one micrometer to tens of micrometers. The isoelectric point of CMCh microgels was determined as pH 4.4. Biocompatibility of CMCh microgels was verified on L929 fibroblasts with 96.5 ± 1.5% cell viability at 1 mg/mL concentration. The drug-carrying abilities of CMCh microgels were evaluated by loading Vancomycin (Van) antibiotic as a model drug. Furthermore, the antibacterial activity efficiency of Van-loaded CMCh microgels (Van@CMCh) was investigated. The MIC values of the released drug from Van@CMCh microgels were found to be 68.6 and 7.95 µg/mL against E. coli and S. aureus, respectively, at 24 h contact time. Disk diffusion tests confirmed that Van@CMCh microgels, especially for Gram-positive (S. aureus) bacteria, revealed long-lasting inhibitory effects on bacteria growth up to 72 h.

In situ forming alginate/gelatin hybrid hydrogels containing doxorubicin loaded chitosan/AuNPs nanogels for the local therapy of breast cancer

In this study, pH-sensitive in situ gelling hydrogels based on oxidized alginate and gelatin-containing doxorubicin (DOX) loaded chitosan/gold nanoparticles (CS/AuNPs) nanogels were fabricated via Schiff-base bond formation. The obtained CS/AuNPs nanogels indicated a size distribution of about 209 nm with a zeta potential of +19.2 mV and an encapsulation efficiency of around 72.6 % for DOX. The study of the rheological properties of hydrogels showed that the value of G' is higher than G″ for all hydrogels, which confirms the elastic behavior of hydrogels in the applied frequency range. The rheological and texture analysis demonstrated the higher mechanical properties of hydrogels containing β-GP and CS/AuNPs nanogels. The release profile of DOX after 48 h indicates the 99 % and 73 % release amount at pH = 5.8 and pH = 7.4, respectively. MTT cytotoxicity study showed that the prepared hydrogels are cytocompatible on MCF-7 cells. By the Live/Dead assay, it was demonstrated that the cultured cells on DOX-free hydrogels were almost alive in the presence of CS/AuNPs nanogels. However, the hydrogel-containing drug and free DOX in the same concentration caused high death of MCF-7 cells as expected, which showed the potential of the developed hydrogels for application in the local treatment of breast cancer.

Recent Advances of Ocular Drug Delivery Systems: Prominence of Ocular Implants for Chronic Eye Diseases

Chronic ocular diseases can seriously impact the eyes and could potentially result in blindness or serious vision loss. According to the most recent data from the WHO, there are more than 2 billion visually impaired people in the world. Therefore, it is pivotal to develop more sophisticated, long-acting drug delivery systems/devices to treat chronic eye conditions. This review covers several drug delivery nanocarriers that can control chronic eye disorders non-invasively. However, most of the developed nanocarriers are still in preclinical or clinical stages. Long-acting drug delivery systems, such as inserts and implants, constitute the majority of the clinically used methods for the treatment of chronic eye diseases due to their steady state release, persistent therapeutic activity, and ability to bypass most ocular barriers. However, implants are considered invasive drug delivery technologies, especially those that are nonbiodegradable. Furthermore, in vitro characterization approaches, although useful, are limited in mimicking or truly representing the in vivo environment. This review focuses on long-acting drug delivery systems (LADDS), particularly implantable drug delivery systems (IDDS), their formulation, methods of characterization, and clinical application for the treatment of eye diseases.

Nanoparticle approaches for the renin-angiotensin system

The renin-angiotensin system (RAS) is a hormonal cascade that contributes to several disorders: systemic hypertension, heart failure, kidney disease, and neurodegenerative disease. Activation of the RAS can promote inflammation and fibrosis. Drugs that target the RAS can be classified into 3 categories, AT1 angiotensin receptor blockers (ARBs), angiotensin-converting enzyme (ACE) inhibitors, and renin inhibitors. The therapeutic efficacy of current RAS-inhibiting drugs is limited by poor penetration across the blood-brain barrier, low bioavailability, and to some extent, short half-lives. Nanoparticle-mediated drug delivery systems (DDSs) are possible emerging alternatives to overcome such limitations. Nanoparticles are ideally 1-100 nm in size and are considered efficient DDSs mainly due to their unique characteristics, including water dispersity, prolonged half-life in blood circulation, smaller size, and biocompatibility. Nano-scale DDSs can reduce the drug dosage frequency and acute toxicity of drugs while enhancing therapeutic success. Different types of nanoparticles, such as chitosan, polymeric, and nanofibers, have been examined in RAS-related studies, especially in hypertension, cardiovascular disease, and COVID-19. In this review article, we summarize the physical and chemical characteristics of each nanoparticle to elaborate on their potential use in RAS-related nano-drug delivery research and clinical application.

Applications and perspectives of quaternized cellulose, chitin and chitosan: A review

Recently, increasing attention has been paid to natural polysaccharides for their low cost, biocompatibility and biodegradability. Quaternization is a modification method to improve the solubility and antibacterial ability of natural polysaccharides. Water-soluble derivatives of cellulose, chitin and chitosan offer the prospect of diverse applications in a wide range of fields, such as antibacterial products, drug delivery, wound healing, sewage treatment and ion exchange membranes. By combining the inherent properties of cellulose, chitin and chitosan with the inherent properties of the quaternary ammonium groups, new products with multiple functions and properties can be obtained. In this review, we summarized the research progress in the applications of quaternized cellulose, chitin and chitosan in recent five years. Moreover, ubiquitous challenges and personal perspectives on the further development of this promising field are also discussed.

Carbohydrate polymer-based bioadhesive formulations and their potentials for the treatment of ocular diseases: A review

Eyes are directly exposed to the outer environment and susceptible to infections, leading to various ocular disorders. Local medication is preferred to treat eye diseases due to its convenience and compliance. However, the rapid clearance of the local formulations highly limits the therapeutic efficacy. In the past decades, several carbohydrate bioadhesive polymers (CBPs), such as chitosan and hyaluronic acid, have been used in ophthalmology for sustained ocular drug delivery. These CBP-based delivery systems have improved the treatment of ocular diseases to a large extent but also caused some undesired effects. Herein, we aim to summarize the applications of some typical CBPs (including chitosan, hyaluronic acid, cellulose, cyclodextrin, alginate and pectin) in treating ocular diseases from the general view of ocular physiology, pathophysiology and drug delivery, and to provide a comprehensive understanding of the design of the CBP-based formulations for ocular use. The patents and clinical trials of CBPs for ocular management are also discussed. In addition, a discussion on the concerns of CBPs in clinical use and the possible solutions is presented.

Timolol-loaded ethosomes for ophthalmic delivery: Reduction of high intraocular pressure in vivo

The beta-adrenoceptor blocker timolol maleate (TML) is a commonly used pharmaceutical agent for the management of glaucoma. Conventional eye drops have limitations due to biological or pharmaceutical factors. Therefore, TML-loaded ethosomes have been designed to mitigate these restrictions and give a viable solution for reducing elevated intraocular pressure (IOP). The ethosomes were prepared using the thin film hydration method. Integrating the Box-Behnken experimental strategy, the optimal formulation was identified. The physicochemical characterization studies were performed on the optimal formulation. Then, in vitro release and ex vivo permeation studies were conducted. The irritation assessment was also carried out with Hen's Egg Test-Chorioallantoic Membrane model (HET-CAM), and in vivo evaluation of the IOP lowering effect was also performed on rats. The physicochemical characterization studies demonstrated that the components of the formulation were compatible with each other. The particle size, zeta potential, and encapsulation efficiency (EE%) were found as 88.23 ± 1.25 nm, -28.7 ± 2.03 mV, and 89.73 ± 0.42 %, respectively. The in vitro drug release mechanism was found as Korsmeyer-Peppas kinetics (R²=0.9923). The HET-CAM findings verified the formulation's eligibility for biological applications. The IOP measurements revealed no statistical difference (p>0.05) between the once-a-day application of the optimal formulation and the three-times-a-day application of the conventional eye drop. A similar pharmacological response was observed at lowered application frequencies. Therefore, it was concluded that the novel TML-loaded ethosomes could be a safe and efficient alternative for glaucoma treatment.

Advances in innovative delivery systems for antiglaucoma drugs

PURPOSE OF REVIEW

Currently, glaucoma treatment drugs are facing problems such as low bioavailability, poor patient compliance, discontinuous administration affecting the efficacy of intraocular pressure (IOP) lowering and chronic damage to the eye caused by side effects of drugs. In order to solve these problems and to better meet clinical needs, various new dosage forms have been developed and applied in the clinical setting.

RECENT FINDINGS

A number of nano formulations and extended-release gels are in successive animal trials, some tear plugs, implants and contact lenses are in clinical trials, and it is believed that more new carrier materials and formulations to improve the bioavailability of drugs are being developed.

SUMMARY

Novel delivery systems for antiglaucoma drugs offer patients more and better therapeutic options, and ongoing or completed studies are providing clear directions for subsequent research to improve clinical applications.

Chitosan-based multifunctional hydrogel for sequential wound inflammation elimination, infection inhibition, and wound healing

In this study, a composite hydrogel (QMPD hydrogel) composed of methacrylate anhydride (MA) grafted quaternary ammonium chitosan (QCS-MA), polyvinylpyrrolidone (PVP), and dopamine (DA) was designed for the sequential wound inflammation elimination, infection inhibition, and wound healing. The QMPD hydrogel formation was initiated by the ultraviolet light-triggered polymerization of QCS-MA. Furthermore, hydrogen bonds, electrostatic interactions, and "π-π" stacking between QCS-MA, PVP, and DA were involved in the hydrogel formation. In this hydrogel, the quaternary ammonium groups of quaternary ammonium chitosan and the photothermal conversion of polydopamine are capable of killing bacteria on wounds, which showed the bacteriostatic ratios of 85.6 % and 92.5 % toward Escherichia coli and Staphylococcus aureus, respectively. Moreover, the oxidation of DA sufficiently scavenged free radicals and introduced the QMPD hydrogel with good anti-oxidant and anti-inflammatory abilities. Together with the extracellular matrix-mimic tropical structure, the QMPD hydrogel significantly promoted the wound management of mice. Therefore, the QMPD hydrogel is expected to provide a new method for the design of wound healing dressings.

Multi-responsive chitosan-based hydrogels for controlled release of vincristine

As medical research progresses, the derivation and development of biological materials such as hydrogels have steadily gained more interest. The biocompatibility and non-toxicity of chitosan make chitosan hydrogels potential carriers for drug delivery. This work aims to develop two multi-reactive, safe, and highly swellable bio-hydrogels consisting of chitosan-graft-glycerol (CS-g-gly) and carboxymethyl chitosan-graft-glycerol (CMCS-g-gly), for sustained and controlled drug release, improved bioavailability along with entrapment in nanocarriers, which reduces side effects of vincristine sulphate. CS-g-gly and CMCS-g-gly are successfully prepared and fully characterized using analytical techniques. Under various conditions, the prepared hydrogels exhibit a high swelling ratio. Vincristine-loaded CS-g-gly (VCR/CS-g-gly), and CMCS-g-gly (VCR/CMCS-g-gly) show high encapsulation efficiency between 72.28-89.97%, and 56.97-71.91%, respectively. VCR/CS-g-gly show a sustained release behavior, and the maximum release of VCR from hydrogels reached 82% after 120 h of incubation. MCF-7 (breast cancer cell line) and MCF-10 (normal breast cell line) are evaluated for cell viability and apoptosis induction. The in-vitro anti-tumor efficacy is investigated using flow cytometry. The tetrazolium-based MTT assay of hydrogels shows no evidence of significant cytotoxicity in MCF-7 and MCF-10 cells. According to these findings, these hydrogels can effectively deliver drugs to MCF-7 and other breast cancer cells.

Preparation and performance of latanoprost-loaded hydrogels as a lacrimal suppository for the treatment of glaucoma

Glaucoma is the leading cause of irreversible blindness, and its treatment is attracting widespread attention. Drug-loaded lacrimal suppositories can effectively treat xerophthalmia, but there is little research on the treatment of glaucoma with drug-loaded lacrimal suppositories. This article explored and expanded the non-pharmacological model of lacrimal suppository therapy for glaucoma by using a combination of lacrimal suppository and medication. The drug-loaded lacrimal suppository was rationally designed through the conjugation of gelatin with polyamide (PAM) via the formation of amide linkages, followed by Schiff base reaction grafting with latanoprost. In vitro drug release studies showed that latanoprost released from drug-loaded lacrimal embolus had sustained-release properties with a release time of 33 days and a drug release volume of 82.6%. The biological evaluation of drug-loaded lacrimal thrombus was carried out by IOP test, retinal potential test, and retinal H&E staining. The results showed that the IOP decreased to 27.125 ± 1.1254 mmHg, and the a and b waves of retinal potential increased to 4.39 ± 0.16 μV and 67.9 ± 2.17 μV, respectively. It indicated that latanoprost lacrimal suppository has a good therapeutic effect on glaucoma.

Microemulsions as Lipid Nanosystems Loaded into Thermoresponsive In Situ Microgels for Local Ocular Delivery of Prednisolone

This study aimed to develop and evaluate thermoresponsive in situ microgels for the local ocular delivery of prednisolone (PRD) (PRD microgels) to improve drug bioavailability and prolong ocular drug residence time. Lipid nanosystems of PRD microemulsions (PRD-MEs) were prepared and evaluated at a drug concentration of 0.25-0.75%. PRD microgels were prepared by incorporating PRD-MEs into 10 and 12% Pluronic^® F127 (F127) or combinations of 12% F127 and 1-10% Kolliphor^®P188 (F68). PRD microgels were characterized for physicochemical, rheological, and mucoadhesive properties, eye irritation, and stability. Results showed that PRD-MEs were clear, miscible, thermodynamically stable, and spherical with droplet size (16.4 ± 2.2 nm), polydispersity index (0.24 ± 0.01), and zeta potential (-21.03 ± 1.24 mV). The PRD microgels were clear with pH (5.37-5.81), surface tension (30.96-38.90 mN/m), size, and zeta potential of mixed polymeric micelles (20.1-23.9 nm and -1.34 to -10.25 mV, respectively), phase transition temperature (25.3-36 °C), and gelation time (1.44-2.47 min). The FTIR spectra revealed chemical compatibility between PRD and microgel components. PRD microgels showed pseudoplastic flow, viscoelastic and mucoadhesive properties, absence of eye irritation, and drug content (99.3 to 106.3%) with a sustained drug release for 16-24 h. Microgels were physicochemically and rheologically stable for three to six months. Therefore, PRD microgels possess potential vehicles for local ocular delivery.

Formulation, In Vitro Characterization and Antibacterial Activity of Chitosan-Decorated Cream Containing Bacitracin for Topical Delivery

(1) Background: Bacitracin is a broad spectrum antibiotic that is used against various microorganisms. Chitosan is a natural polymer that has been widely investigated as an antimicrobial agent for preventing and treating infections owing to its intrinsic antimicrobial properties, as well as its ability to effectively deliver extrinsic antimicrobial compounds to infected areas. Topical drug delivery offers important benefits for improving the therapeutic effect and reducing systemic side effects of administered compounds/drugs. The topical use of chitosan-decorated bacitracin-loaded cream improves the permeation of the drug across the skin and enhances the drug bioavailability by prolonging the residence time of the drug when applied topically, as well as producing synergistic effects and reducing the side effects of the drug. Topical chitosan-decorated cream can be a promising approach to administer the drug more efficiently and enhance the efficacy of treatment in wound healing and antibacterial activity. (2) Methods: This study was conducted to prepare, assess and investigate the synergistic antibacterial activity of a chitosan-coated bacitracin cream. The results were compared to the antibacterial activity of simple bacitracin-loaded cream. The prepared cream was evaluated for various in vitro characteristics such as rheology, pH, viscosity, drug content and antibacterial activity studies. (3) Result: The formulations were found to be stable regarding color, liquefaction and phase separation at all accelerated conditions. It was observed that with time, substantial variations in the pH of the preparations were found. The introduction of chitosan results in controlled release of the drug from the formulations. The antibacterial activity of the formulated creams was assessed with the disc diffusion method against Staphylococcus aureus(ATCC),Escherichiacoli (STCC),Pseudomonas aeruginosa(ATCC) and Bacillus cereus(ATCC). The strains, E. coli, S. aureus, P. aeruginosa and B. cereus were susceptible to 50 µg chitosan-decorated bacitracin cream, showing inhibition zones of 10 ± 0.6, 34 ± 1.5, 31 ± 0.76 and 21 ± 2.02 mm, respectively. The zones of inhibition for simple bacitracin-loaded cream were significantly smaller than chitosan-decorated cream, at 2 ± 0.2, 28 ± 0.92, 15 ± 0.5 and 11 ± 1.25 mm (ANOVA; p < 0.05), respectively. (4) Conclusion: It was observed that the zones of inhibition of simple bacitracin-loaded cream were significantly smaller than those of chitosan-decorated bacitracin-loaded cream. Chitosan synergistically improves the antimicrobial activity of bacitracin. Hence, the developed formulation was effective and should be considered as a suitable candidate for topical management of skin infections and wound healing.

Glaucoma Treatment and Hydrogel: Current Insights and State of the Art

Aqueous gels formulated using hydrophilic polymers (hydrogels) and those based on stimuli-responsive polymers (in situ gelling or gel-forming systems) attract increasing interest in the treatment of several eye diseases. Their chemical structure enables them to incorporate various ophthalmic medications, achieving their optimal therapeutic doses and providing more clinically relevant time courses (weeks or months as opposed to hours and days), which will inevitably reduce dose frequency, thereby improving patient compliance and clinical outcomes. Due to its chronic course, the treatment of glaucoma may benefit from applying gel technologies as drug-delivering systems and as antifibrotic treatment during and after surgery. Therefore, our purpose is to review current applications of ophthalmic gelling systems with particular emphasis on glaucoma.

Evaluation of quaternization effect on chitosan-HAP composite for bone tissue engineering application

This study attempts to improve the aqueous solubility of chitosan and utilizes it in the fabrication of composites with hydroxyapatite (HAP). The composites were evaluated as a curcumin delivery vehicle for bone regeneration. The chitosan was modified by quaternization, with a quaternization degree of 5 % for low quaternized chitosan (LQC) and 11 % for high quaternized chitosan (HQC). The modified chitosan, at alkaline pH 11, facilitated in situ HAP growth and formed LQC-HAP and HQC-HAP composites. The quaternization weakens intermolecular hydrogen bonds, facilitates interaction with the apatite precursor ions and promotes the growth of HAP. The modification significantly improved drug encapsulation (2.6 fold) but at the cost of a slight decrease in mechanical strength and increase in drug release. The in vitro studies with human osteoblast-like MG-63 cells established that the curcumin-loaded composites, LQC-HAP-C and HQC-HAP-C are biocompatible, encourage proliferation and promote a 2-fold increase in calcium mineralization over drug-free composites. The study exemplifies the reciprocity between quaternization degree and drug load/release properties and also illustrates that the magnitude of the latter reflects bioactivity. Thus, the quaternized chitosan-based HAP composite with tailorable bio-physicochemical properties becomes an interesting drug delivery system in bone regeneration.

Fabrication of Janus-type nanocomposites from cellulose nanocrystals for self-healing hydrogels' flexible sensors

Janus bio-nanomaterials have great application potential in functional solid surfactants, probes and flexible sensors. In this manuscript, the sustainable Janus cellulose nanocrystals-type (CNCs-type) nanomaterials were prepared by Pickering emulsion template method. The asymmetric functionalism of Janus nanorods was realized by asymmetrically grafting polypyrrole (PPy) and polydopamine (PDA) onto different sides of CNCs (Janus CNCs-PPy /PDA (JCNs)). JCNs was successfully applied to self-healing nanocomposite hydrogels and further applied to the development of flexible sensors. The self-healing efficiency of nanocomposite hydrogels was 87.2%, and the stress and strain reached 3.50 MPa and 453.45%, respectively. It is worth noting that flexible sensors have been widely used in the field of wearable electronic sensing for real-time monitoring of human movement due to their high sensitivity (gauge factor (GF) = 9.9) and fast response time (260 ms).

Novel Gels: An Emerging Approach for Delivering of Therapeutic Molecules and Recent Trends

Gels are semisolid, homogeneous systems with continuous or discrete therapeutic molecules in a suitable lipophilic or hydrophilic three-dimensional network base. Innovative gel systems possess multipurpose applications in cosmetics, food, pharmaceuticals, biotechnology, and so forth. Formulating a gel-based delivery system is simple and the delivery system enables the release of loaded therapeutic molecules. Furthermore, it facilitates the delivery of molecules via various routes as these gel-based systems offer proximal surface contact between a loaded therapeutic molecule and an absorption site. In the past decade, researchers have potentially explored and established a significant understanding of gel-based delivery systems for drug delivery. Subsequently, they have enabled the prospects of developing novel gel-based systems that illicit drug release by specific biological or external stimuli, such as temperature, pH, enzymes, ultrasound, antigens, etc. These systems are considered smart gels for their broad applications. This review reflects the significant role of advanced gel-based delivery systems for various therapeutic benefits. This detailed discussion is focused on strategies for the formulation of different novel gel-based systems, as well as it highlights the current research trends of these systems and patented technologies.

Imaging Methods for the Assessment of a Complex Hydrogel as an Ocular Drug Delivery System for Glaucoma Treatment: Opportunities and Challenges in Preclinical Evaluation

Glaucoma is one of the leading causes of loss of vision. The problems associated with the marketed formulations of anti-glaucoma drugs are low bioavailability, unwanted side effects, and low patient compliance. Hydrogels are an important class of soft materials that play a crucial role in developing an ocular drug delivery system. They assume a special significance in addressing the problems associated with the marketed formulations of eyedrops. An appropriate design of the hydrogel system capable of encapsulating single or multiple drugs for glaucoma has emerged in recent times to overcome such challenges. Although various modes of imaging play critical roles in assessing the efficacy of these formulations, evaluating hydrogels for drug permeation and retention remains challenging. Especially, the assessment of dual drugs in the hydrogel system is not straightforward due to the complexity in measuring drug penetration and retention for in vivo or ex vivo systems. There is a need to develop tools for the fabrication and validation of hydrogel-based systems that give insight into precorneal retention, biocompatibility, cellular uptake, and cell permeation. The current review highlights some of the complexities in formulating hydrogel and benchmarking technologies, including confocal laser scanning microscopy, fluorescent microscopy, slit-lamp biomicroscopy, and camera-based imaging. This review also summarizes recent evaluations of various hydrogel formulations using in vitro and in vivo models. Further the article will help researchers from various disciplines, including formulation scientists and biologists, set up preclinical protocols for evaluating polymeric hydrogels.

Bioactive Chitosan-Based Organometallic Scaffolds for Tissue Engineering and Regeneration

Captivating achievements in developing advanced hybrid biostructures through integrating natural biopolymers with inorganic materials (e.g., metals and metalloids) have paved the way towards the application of bioactive organometallic scaffolds (OMSs) in tissue engineering and regenerative medicine (TERM). Of various biopolymers, chitosan (CS) has been used widely for the development of bioactive OMSs, in large part due to its unique characteristics (e.g., biocompatibility, biodegradability, surface chemistry, and functionalization potential). In integration with inorganic elements, CS has been used to engineer advanced biomimetic matrices to accommodate both embedded cells and drug molecules and serve as scaffolds in TERM. The use of the CS-based OMSs is envisioned to provide a new pragmatic potential in TERM and even in precision medicine. In this review, we aim to elaborate on recent achievements in a variety of CS/metal, CS/metalloid hybrid scaffolds, and discuss their applications in TERM. We also provide comprehensive insights into the formulation, surface modification, characterization, biocompatibility, and cytotoxicity of different types of CS-based OMSs.

Synergistic Effect of Acetazolamide-(2-hydroxy)propyl β-Cyclodextrin in Timolol Liposomes for Decreasing and Prolonging Intraocular Pressure Levels

The purpose of this study was to design, for the first time, a co-loaded liposomal formulation (CLL) for treatment of glaucoma including timolol maleate (TM) in the lipid bilayer and acetazolamide (Acz)-(2-hydroxy)propyl β-cyclodextrin (HPβCD) complexes (AczHP) solubilized in the aqueous core of liposomes. Formulations with TM (TM-L) and AczHP (AczHP-L), separately, were also prepared and characterized. A preliminary study comprising the Acz/HPβCD complexes and their interaction with cholesterol (a component of the lipid bilayer) was realized. Then, a screening study on formulation factors affecting the quality of the product was carried out following the design of the experiment methodology. In addition, in vitro release and permeation studies and in vivo lowering intraocular pressure (IOP) studies were performed. The results of the inclusion complexation behavior, characterization, and binding ability of Acz with HPβCD showed that HPβCD could enhance the water solubility of Acz despite the weak binding ability of the complex. Ch disturbed the stability and solubility parameters of Acz due to the fact of its competence by CD; thus, Chems (steroid derivative) was selected for further liposome formulation studies. The optimization of the lipid bilayer composition (DDAB, 0.0173 mmol and no double loading) and the extrusion as methods to reduce vesicle size were crucial for improving the physico-chemical properties and encapsulation efficiency of both drugs. In vitro release and permeation studies demonstrated that the CLL formulation showed improvement in in vitro drug release and permeation compared to the liposomal formulations with a single drug (TM-L and AczHP-L) and the standard solutions (TM-S and AczHP-S). CLL showed high efficacy in reducing and prolonging IOP, suggesting that the synergistic effect of TM and Acz on aqueous humor retention and the presence of this cyclodextrin and liposomes as permeation enhancers are responsible for the success of this strategy of co-loading for glaucoma therapy.

Chitosan for biomedical applications, promising antidiabetic drug delivery system, and new diabetes mellitus treatment based on stem cell

Since chitosan's excellent pharmacokinetic and chemical properties, it is an attractive and promising carbohydrate biopolymer in biomedical applications. Chitosan's beneficial function in the defense and propagation of pancreatic β cells, reducing hyperglycemia, and avoiding diabetes mellitus associated with impaired lipid metabolism has been demonstrated in several studies. Additionally, chitosan has also been used in various nanocarriers to deliver various antidiabetic drugs to reduce glucose levels. Herein, the first to provide the currently available potential benefits of chitosan in diabetes mellitus treatment focuses on chitosan-based nanocarriers for oral administration of various antidiabetic drugs nasal and subcutaneous passages. Moreover, chitosan is used to activate and deliver stem cells and differentiate them into cells similar to pancreatic beta cells as a new type of treatment for type one diabetes mellitus. The results of this review will be helpful in the development of promising treatments and better control of diabetes mellitus.

Designing robust chitosan-based hydrogels for stem cell nesting under oxidative stress

Introduction: Hydrogels are unique candidates for a wide range of biomedical applications including drug delivery and tissue engineering. The present investigation was designed to consider the impact of chitosan-based hydrogels as a scaffold on the proliferation of human bone marrow mesenchymal stem cells (hBM-MSCs) besides neutralization of oxidative stress in hBM-MSCs. Methods: Chitosan (CS) and CS-gelatin hydrogels were fabricated through ionic crosslinking using β-glycerophosphate. The hBM-MSCs were cultured on the prepared matrices and their proliferation was evaluated using DAPI staining and MTT assay. Furthermore, the effect of hydrogels on oxidative stress was assessed by measuring the expression of NQO1, Nrf2, and HO-1 genes using real-time PCR. Results: The developed hydrogels indicated a porous structure with high water content. The toxicity studies showed that the prepared hydrogels have a high biocompatibility/cytocompatibility. The expression of intracellular antioxidant genes was studied to ensure that stress is not imposed by the scaffold on the nested cells. The results showed that Nrf2 as a super transcription factor of antioxidant genes and its downstream antioxidant gene, NQO1 were downregulated. Unexpectedly, the upregulation of HO-1 was detected in the current study. Conclusion: The prepared CS-based hydrogels with desired properties including porous structure, high swelling ability, and cytocompatibility did not show oxidative stress for the nesting of stem cells. Therefore, they could be attractive scaffolds to support stem cells for successful tissue engineering purposes.

Biomedical Applications of Quaternized Chitosan

The natural polymer chitosan is the second most abundant biopolymer on earth after chitin and has been extensively explored for preparation of versatile drug delivery systems. The presence of two distinct reactive functional groups (an amino group at C2, and a primary and secondary hydroxyl group at C3 and C6) of chitosan are involved in the transformation of expedient derivatives such as acylated, alkylated, carboxylated, quaternized and esterified chitosan. Amongst these, quaternized chitosan is preferred in pharmaceutical industries owing to its prominent features including superior water solubility, augmented antimicrobial actions, modified wound healing, pH-sensitive targeting, biocompatibility, and biodegradability. It has been explored in a large realm of pharmaceuticals, cosmeceuticals, and the biomedical arena. Immense classy drug delivery systems containing quaternized chitosan have been intended for tissue engineering, wound healing, gene, and vaccine delivery. This review article outlines synthetic techniques, basic characteristics, inherent properties, biomedical applications, and ubiquitous challenges associated to quaternized chitosan.

Size-dependent thermo-mechanical vibration of lipid supramolecular nano-tubules via nonlocal strain gradient Timoshenko beam theory

Nowadays, nanostructured lipid carriers are used as carrier systems to control the release of drug molecules and promote their physicochemical stability. A better understanding of the dynamic behavior of lipid nano-tubules can facilitate a better drug delivery and other relevant applications. The dynamic behaviors of these lipid nano-tubules are susceptible to temperature variations. Hence, a deeper insight into these effects, as mentioned above, is necessary to ensure higher analysis efficiency. However, the models used in previous researches did not take into account these effects. The lipid nano-tubules often possess a small length-to-width ratio and as a result, the use of the Euler-Bernoulli beam theory for modeling them will significantly reduce the accuracy of calculations, in which Timoshenko beam model is used to increase the accuracy of the model. The main objective of the current study is to investigate the bending vibrations of lipid nano-tubules by considering the temperature effects based on nonlocal strain gradient theory. To this end, based on Hamilton's principle, the governing equations of a dynamical system were extracted by taking into account the temperature effects. The equations were solved using the Navier solution method. Moreover, the dimensionless natural frequency and critical temperature of the lipid nano-tubules were calculated. Our findings demonstrate that the critical temperature is a function of the nonlocal parameter and length-scale parameter variations. It is also observed that at a certain interval of the length scale parameter, increasing the value of the nonlocal parameter results in intensification of the hardening behavior of lipid nano-tubules. Based on our findings, the proposed model indicates good accuracy and prediction.

Fabrication and characterization of an injectable reinforced composite scaffold for cartilage tissue engineering: an in vitro study

There are limitations in current medications of articular cartilage injuries. Although injectable bioactive hydrogels are promising options, they have decreased biomechanical performance. Researchers should consider many factors when providing solutions to overcome these challenges. In this study, we created an injectable composite hydrogel from chitosan and human acellular cartilage extracellular matrix (ECM) particles. In order to enhance its mechanical properties, we reinforced this hydrogel with microporous microspheres composed of the same materials as the structural building blocks of the scaffold. Articular cartilage from human donors was decellularized by a combination of physical, chemical, and enzymatic methods. The decellularization efficiency was assessed by histological analysis and assessment of DNA content. We characterized the composite constructs in terms of storage modulus, gelation time, biocompatibility, and differentiation potential. The results showed that mechanical behavior increased with an increase in microsphere content. The sample that contained 10% microsphere had an enhanced storage modulus of up to 90 kPa. Biocompatibility and preliminary differentiation investigations revealed that this composite hydrogel might have potential benefits for cartilage tissue engineering.

Development of a dual delivery of levofloxacin and prednisolone acetate via PLGA nanoparticles/ thermosensitive chitosan-based hydrogel for postoperative management: An in-vitro and ex-vivo study

Post-operative endophthalmitis (POE) is one of the most dreadful complications after intraocular surgery. For cataract surgery patients, both commercially available topical 0.5% levofloxacin and 1% prednisolone acetate (PA) ophthalmic solution require at least 3 to 4 times application daily. In this study, we develop a dual drug delivery system composed of the thermosensitive chitosan/gelatin-based hydrogel containing PA and levofloxacin-loaded nanoparticles (LNPs). LNPs with negative surface charge show the monodisperse (polydispersity index ~0.045), nanosize (~154.7 nm) and sphere-like structure. The optimal concentration of LNPs and PA to corneal epithelial cells was 5 μg/mL and 50 μg/mL, respectively. The developed dual drug delivery system (PAgel-LNPs) could gel at 34 °C within 63 s. The osmolarity of PAgel-LNPs was 301.2 ± 1.5 mOsm/L. PAgel-LNPs showed a sustained-release profile for 7 days. Post-treatment of PAgel-LNPs in TNF-α-damaged corneal epithelial cells could decrease the inflammation (inflammatory genes (TNF-α, IL-6, MMP-3 andMMP-9) and IL-6 production) and cell death. In ex-vivo rabbit model of S. aureus keratitis, the anti-inflammation and anti-bacterial property have been demonstrated. These results suggest that thermosensitive PAgel-LNPs may have the potential to use for the prevention of POE.

Preparation of chitosan/hydrolyzed collagen/hyaluronic acid based hydrogel composite with caffeic acid addition

In this work, biopolymer hydrogels were synthesized by mixing hyaluronic acid, hydrolyzed collagen, and chitosan through a solvent evaporation method and incorporating them with caffeic acid as an antioxidant agent. The obtained caffeic acid-loaded chitosan/hydrolyzed collagen/hyaluronic acid hydrogels were characterized by X-ray diffraction, differential scanning calorimetry and thermogravimetric analysis. No significant change on structural and thermal properties was observed. Furthermore, scanning electron microscope reported that the surface morphology of the hydrogels was smooth, and no significant change in porosity was observed after the addition of hyaluronic acid. With high amount of hyaluronic acid, the swelling behaviour was superiority. The hydrogels showed an initial burst release of caffeic acid (~70%) within 60 min, followed by a gradual release of up to 80% by 480 min. The release was slightly higher with the presence of hyaluronic acid. In addition, DPPH, ABTS⁺, and FRAP assays revealed that the caffeic acid-loaded hyaluronic acid/hydrolyzed collagen/chitosan hydrogels exhibited antioxidant activity. Thus, these composites could potentially be used as dressing materials with antioxidant activity.

Regulation of the Ocular Cell/Tissue Response by Implantable Biomaterials and Drug Delivery Systems

Therapeutic advancements in the treatment of various ocular diseases is often linked to the development of efficient drug delivery systems (DDSs), which would allow a sustained release while maintaining therapeutic drug levels in the target tissues. In this way, ocular tissue/cell response can be properly modulated and designed in order to produce a therapeutic effect. An ideal ocular DDS should encapsulate and release the appropriate drug concentration to the target tissue (therapeutic but non-toxic level) while preserving drug functionality. Furthermore, a constant release is usually preferred, keeping the initial burst to a minimum. Different materials are used, modified, and combined in order to achieve a sustained drug release in both the anterior and posterior segments of the eye. After giving a picture of the different strategies adopted for ocular drug release, this review article provides an overview of the biomaterials that are used as drug carriers in the eye, including micro- and nanospheres, liposomes, hydrogels, and multi-material implants; the advantages and limitations of these DDSs are discussed in reference to the major ocular applications.