Preparation and drug release behavior of pH-responsive bovine serum albumin-loaded chitosan microspheres

Enhanced siRNA delivery with novel smart chitosan-based formulations

This study aims to develop an innovative multifunctional and dual responsive drug formulation for precise siRNA delivery to breast cancer sites, addressing the challenges posed by conventional cancer treatments which often result in adverse side effects due to their non-specific nature. The formulation made by incorporating gold coated superparamagnetic iron oxide nanoparticles (Au-SPIONs) into chitosan microspheres, which were subsequently loaded with siRNA. Comprehensive characterization, including scanning electron microscopy (SEM), transmission electron microscopy (TEM), dynamic light scattering (DLS), Fourier-transform infrared spectroscopy (FTIR), and energy-dispersive X-ray spectroscopy (EDS) confirmed the formulation's favourable morphology, particle size distribution, chemical composition, and stability, indicating its strong potential for effective siRNA drug delivery applications. The developed formulation demonstrated siRNA encapsulation efficiencies ranging from 27.4 % to 88.6 % and loading capacity from 0.291 % to 1.59 %, these values particularly higher for medium molecular weight chitosan. These results were compared across different formulations, showing that variations in chitosan type and crosslinker concentration significantly influenced encapsulation efficiency and drug release profiles. Additionally, our results were compared to previous studies on chitosan microspheres encapsulating organic drugs and siRNA, where the developed system demonstrated similar encapsulation and release properties.. The type of chitosan and the choice of crosslinker significantly influenced the drug release patterns. Diverse release profiles across batches highlighted the necessity for precise formulation control. Incorporating SPIONs into chitosan microspheres presents a promising strategy for magnetically driven, site-specific drug delivery. The dual pH-responsive and magnetic properties enable rapid and targeted siRNA release, leveraging the acidic tumor microenvironment as an internal stimulus in addition to external magnetic stimuli. This novel combination of SPIONs, chitosan microspheres, and siRNA encapsulation represents a new approach for targeted drug delivery. While further research is needed to refine and optimize this approach, our study provides a proof of concept for advancing targeted cancer therapies.

PAD4 Inhibitor-Loaded Magnetic Fe3O4 Nanoparticles for Magnetic Targeted Chemotherapy and Magnetic Resonance Imaging of Lung Cancer

Introduction

Lung cancer is a major health concern worldwide owing to its high incidence and mortality rates. Therefore, identification of new therapeutic targets and strategies for lung cancer is critical for improving patient outcomes. Peptidyl arginine deiminase 4 (PAD4) promotes tumor growth and metastasis by catalyzing the citrullination of histones, making it a potential therapeutic target. Although PAD4 inhibitors have shown potential in the treatment of a variety of tumors, existing PAD4 inhibitors lack sufficient specificity and cause substantial systemic adverse reactions. To overcome these challenges, we developed novel YW403@Fe3O4-oxidized carboxymethyl chitosan (OCMC) magnetic nanoparticles (MNPs) that enabled magnetically targeted drug delivery by binding the PAD4 inhibitor YW403 to a ferric oxide magnetic carrier.

Methods

In vitro experiments were conducted using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assays, Transwell assays, and flow cytometry to evaluate the activity of the MNPs. In vivo experiments involved magnetic resonance imaging (MRI) assessments and inductively coupled plasma mass spectrometry (ICP-MS) analyses to confirm the tumor targeting and iron metabolism of MNPs. Additionally, immunofluorescence staining was employed to further validate the expression of citrullinated histone H3 (H3cit).

Results

The implementation of this approach enhanced the targeting efficiency of PAD4 inhibitors, consequently reducing the required dosage of chemotherapy and potentially facilitating MRI monitoring. In vitro experiments demonstrated that MNPs exhibited superior activity compared to free drugs when subjected to an applied magnetic field, due to increased uptake of MNPs by tumor cells. In vivo experiments revealed that the application of magnetic fields significantly improved the tumor targeting of MNPs without impacting iron metabolism. By suppressing the expression of citrullinated histone (H3cit), MNPs effectively inhibited tumor growth and metastasis.

Discussion

These findings provide new research ideas for the development of novel anti-tumor nanomaterials and are expected to yield breakthroughs in the treatment of lung cancer.

Development of chitosan/hydrolyzed collagen interaction product-based microparticles for the treatment of respiratory tract infections

Respiratory tract infections (RTIs) represent a significant global health issue, particularly for vulnerable population, such as children, the elderly, or patients with immunosuppression. In this context, the aim of the present work was the development of Chitosan/Hydrolyzed Collagen-based microparticles (Mps) as a pulmonary drug delivery system (PDDS) for the treatment of RTIs. Mps were produced via spray-drying and composed of chitosan (Cs), one of the most widely used polysaccharides in PDDS, and hydrolyzed collagen (HC), another promising material for the development of PDDS that has not yet been fully explored. The formation of an interaction product between Cs and HC occurred during the spray-drying process and was confirmed by infrared spectroscopy and thermal analysis. Mps were characterized in terms of morphology, particle size, zeta potential, aerodynamic performance, swelling behavior and biodegradation profile in simulated lung fluid. Mps biocompatibility was also assessed on adenocarcinomic human alveolar basal epithelial (A549) cells. Finally, Mps were characterized in vitro for antibacterial properties and their ability to inhibit bacterial adhesion to S. aureus and P. aeruginosa. An enhanced antibacterial effect was observed for Mps with respect to the pristine materials (Cs and HC) and their physical mixture. Moreover, Mps were also able to inhibit bacteria adhesion to epithelial cells.

Chitosan-melanin complex microsphere: A potential colonic delivery system for protein drugs

The characteristics and performance of chitosan-based colon delivery systems are significantly influenced by the method of preparation. Insect chitosan-melanin complex (CMC) may offer superior attributes over traditional shrimp and crab chitosan (CS) for colon-targeted administration. This study used dung beetle CMC as the carrier matrix and comprehensively examined the impact of various crosslinking techniques on the colonic drug delivery efficacy of microspheres, encompassing drug loading, swelling, drug release behavior, adhesion, enzymatic degradation, and absorption enhancement. The results indicate that F-TPPLC microspheres, crosslinked with a combination of formaldehyde and sodium tripolyphosphate, exhibit superior drug loading capabilities, optimal swelling behavior, and controlled in vitro drug release profiles in the colonic environment, along with excellent adhesion and enzymatic degradation properties within intestinal tract. Notably, these F-TPPLC microspheres increase paracellular permeability, possibly by disrupting the calcium-dependent adhesion junctions. In comparison to commercial CS, CMC demonstrates superior drug encapsulation efficiency, enhanced colonic drug release, adhesion, and absorption promotion, rendering it a favorable candidate as a carrier in colon-targeted drug delivery systems. Consequently, F-TPPLC microspheres derived from CMC are highly suitable for colon drug delivery applications and show promising potential for the oral delivery of peptide and protein-based therapeutics to the colon.

Preparation and characterization of polyphenol-chitosan conjugate-eugenol essential oil microcapsule and its effect on storage behavior of cherry tomato

Given the high volatility, low water solubility, and oxidative sensitivity of essential oils, this study synthesized microcapsules of essential oil (EEO) (quercetin-chitosan-EEO [QE-CS-EEO]) using a QE-CS graft copolymer as the wall material and EEO as the core material. Research findings indicate that QE-CS exhibits superior in vitro antioxidant activity, with scavenging abilities for 2,2-diphenyl-1-picrylhydrazyl and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) ABTS+ radicals being 58.71% and 77.03% greater than those of CS, respectively, thereby providing more effective protection for the essential oil. In comparison to CS essential oil, microcapsules (CS-EEO), QE-CS-EEO demonstrated an 18.65% increase in EEO encapsulation efficiency, achieving a total encapsulation efficiency of 41.29%. Based on these results, various edible coating solutions were formulated, including Control, E1 (1% CS), E2 (0.5% CS + 0.5% CS-EEO), E3 (0.5% CS + 0.5% QE-CS-EEO), and E4 (1% EEO), to extend the shelf life of cherry tomatoes. Notably, cherry tomatoes treated with the E3 formulation maintained superior freshness indicators, exhibiting an extended shelf life of approximately 9-12 days compared to the control group. This study aims to explore a novel microcapsule wall material and provide a strategy for extending the shelf life of fruits and vegetables, thereby minimizing food waste.

Development, optimization, and characterization of polymeric micelles to improve dasatinib oral bioavailability: Hep G2 cell cytotoxicity and in vivo pharmacokinetics for targeted liver cancer therapy

The efficacy of dasatinib (DAS) in treating hepatocellular carcinoma (HCC) is hindered by its poor bioavailability, limiting its clinical potential. In this study, we explored the use of TPGS-Soluplus micelles as an innovative drug delivery platform to enhance DAS solubility, stability, and therapeutic impact. A series of TPGS-Soluplus copolymers were synthesized, varying the D-α-tocopheryl polyethylene glycol succinate (TPGS) forms (1000, 2000, and 3500) and adjusting the TPGS to Soluplus weight ratios (1:1, 1:2, and 1:3). Our goal was to identify the optimal formulation with the highest entrapment efficiency, smallest particle size, and enhanced drug loading. The TPGS1000-Soluplus copolymer, with a DAS-to-polymer ratio of 1:30 and a TPGS ratio of 1:2, demonstrated superior performance, achieving an entrapment efficiency of 64.479 ± 1.45 % and drug loading of 5.05 ± 1.01 %. The DAS-loaded micelles (DAS-PMs) exhibited a notably small particle size of 64.479 ± 1.45 nm and demonstrated controlled release kinetics, with 85.60 ± 5.4 % of the drug released over 72 h. Cellular uptake studies using Hep G2 cells revealed significantly enhanced absorption of DAS-PMs compared to free DAS, reflected in lower IC50 values in MTT assays at 24 and 48 h. Pharmacokinetic analysis further highlighted the benefits of the DAS-PMs, with an AUC0-∞ 2.16 times higher and mean residual time (MRT) 1.3 times longer than free DAS, a statistically significant improvement (p < 0.01). These findings suggest that TPGS-Soluplus micelles offer a promising strategy for improving the bioavailability and efficacy of DAS in HCC treatment, presenting a potential new therapeutic avenue for patients with limited options. This innovative formulation could significantly enhance DAS delivery, potentially leading to improved clinical outcomes in liver cancer therapy.

Development of pH-sensitive chitosan/plant extract microcapsules: Enhanced corrosion protection for carbon steel in HCl solution

In recent years, controlled-release green corrosion inhibitors have become a research hotspot in the field of corrosion. In this study, chitosan/plant extract microcapsules (GCI@CS) loaded with Ambrosia artemisiifolia extract (green corrosion inhibitor, GCI) were prepared by emulsification cross-linking. Both the functional groups and micromorphology of GCI@CS were characterized using Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and optical microscopy (OM). The loading capacity and encapsulation efficiency of GCI@CS were analyzed using UV-Vis spectroscopy. The corrosion inhibition performance of GCI@CS on carbon steel (C-steel) in 1.0 mol/L HCl was investigated using electrochemical impedance spectroscopy (EIS). The results indicated that GCI@CS, as a pH-sensitive microcapsule, can provide effective corrosion protection for C-steel in HCl solution. Notably, the corrosion resistance of GCI@CS improved with increasing concentration and time. The corrosion inhibition efficiency (ηEIS) of C-steel immersed in 1.0 mol/L HCl (with 500 mg/L GCI@CS) for 24 h reached 93.48 %. This study provides important insights for the industrial deployment of green corrosion inhibitors with controlled release properties.

Enhanced fabrication of size-controllable chitosan-genipin nanoparticles using orifice-induced hydrodynamic cavitation: Process optimization and performance evaluation

Chitosan nanoparticles (NPs) possess great potential in biomedical fields. Orifice-induced hydrodynamic cavitation (HC) has been used for the enhancement of fabrication of size-controllable genipin-crosslinked chitosan (chitosan-genipin) NPs based on the emulsion cross-linking (ECLK). Experiments have been performed using various plate geometries, chitosan molecular weight and under different operational parameters such as inlet pressure (1-3.5 bar), outlet pressure (0-1.5 bar) and cross-linking temperature (40-70 °C). Orifice plate geometry was a crucial factor affecting the properties of NPs, and the optimized geometry of orifice plate was with single hole of 3.0 mm diameter. The size of NPs with polydispersity index of 0.359 was 312.6 nm at an optimized inlet pressure of 3.0 bar, and the maximum production yield reached 84.82 %. Chitosan with too high or too low initial molecular weight (e.g., chitosan oligosaccharide) was not applicable for producing ultra-fine and narrow-distributed NPs. There existed a non-linear monotonically-increasing relationship between cavitation number (Cv) and chitosan NP size. Scanning electron microscopy (SEM) test indicated that the prepared NPs were discrete with spherical shape. The study demonstrated the superiority of HC in reducing particle size and size distribution of NPs, and the energy efficiency of orifice type HC-processed ECLK was two orders of magnitude than that of ultrasonic horn or high shear homogenization-processed ECLK. In vitro drug-release studies showed that the fabricated NPs had great potential as a drug delivery system. The observations of this study can offer strong support for HC to enhance the fabrication of size-controllable chitosan-genipin NPs.

Ozonated Sunflower Oil Embedded within Spray-Dried Chitosan Microspheres Cross-Linked with Azelaic Acid as a Multicomponent Solid Form for Broad-Spectrum and Long-Lasting Antimicrobial Activity

Multicomponent solid forms for the combined delivery of antimicrobials can improve formulation performance, especially for poorly soluble drugs, by enabling the modified release of the active ingredients to better meet therapeutic needs. Chitosan microspheres incorporating ozonated sunflower oil were prepared by a spray-drying method and using azelaic acid as a biocompatible cross-linker to improve the long time frame. Two methods were used to incorporate ozonated oil into microspheres during the atomization process: one based on the use of a surfactant to emulsify the oil and another using mesoporous silica as an oil absorbent. The encapsulation efficiency of the ozonated oil was evaluated by measuring the peroxide value in the microspheres, which showed an efficiency of 75.5-82.1%. The morphological aspects; particle size distribution; zeta potential; swelling; degradation time; and thermal, crystallographic and spectroscopic properties of the microspheres were analyzed. Azelaic acid release and peroxide formation over time were followed in in vitro analyses, which showed that ozonated oil embedded within chitosan microspheres cross-linked with azelaic acid is a valid system to obtain a sustained release of antimicrobials. In vitro tests showed that the microspheres exhibit synergistic antimicrobial activity against P. aeruginosa, E. coli, S. aureus, C. albicans and A. brasiliensis. This makes them ideal for use in the development of biomedical devices that require broad-spectrum and prolonged antimicrobial activity.

Enzymatic time-temperature indicator with cysteine-loaded chitosan microspheres/silver nanoparticles

A time-temperature indicator (TTI) based on acid-base reaction was developed by applying a new pH dye composed of cysteine-loaded chitosan (Cys-CS) microspheres and silver nanoparticles (AgNPs). It was hypothesized that cysteine released by the disintegration of Cys-CS microspheres at a critical pH would cause AgNPs to aggregate, leading to color change. Cys-CS microspheres were produced as water-in-oil (paraffin oil, MCT oil, soybean oil) emulsions according to the KOH addition method. An enzymatic TTI was made using glucose oxidase, glucose, and catalase. Only paraffin oil produced Cys-CS microspheres (average diameter, 335 ± 100 µm), whereas the others did not, probably due to saponification with KOH. FTIR analysis confirmed that cysteine was encapsulated in the microspheres. The microspheres disintegrated at pH 6.18 in a titration test. The TTI pH gradually decreased and showed a sudden color change at pH 6.10, which was similar to the critical pH of microsphere disintegration.

Bactericidal Activity of Silver-Doped Chitosan Coatings via Electrophoretic Deposition on Ti6Al4V Additively Manufactured Substrates

Prosthetic reconstruction can serve as a feasible alternative, delivering both functional and aesthetic benefits to individuals with hand and finger injuries, frequent causes of emergency room visits. Implant-related infections pose significant challenges in arthroplasty and osteosynthesis procedures, contributing to surgical failures. As a potential solution to this challenge, this study developed a new class of silver (Ag)-doped chitosan (CS) coatings via electrophoretic deposition (EPD) on osseointegrated prostheses for infection therapy. These coatings were successfully applied to additively manufactured Ti6Al4V ELI samples. In the initial phase, the feasibility of the composite coating was assessed using the Thermogravimetric Analysis (TGA) and Attenuated Total Reflection (ATR) techniques. The optimized structures exhibited impressive water uptake in the range of 300-360%. Codeposition with an antibacterial agent proved effective, and scanning electron microscopy (SEM) was used to examine the coating morphology. Biologically, CS coatings demonstrated cytocompatibility when in direct contact with a fibroblast cell line (L929) after 72 h. When exposed to the Staphylococcus epidermidis strain (ATCC 12228), these coatings inhibited bacterial growth and biofilm formation within 24 h. These findings underscore the significant potential of this approach for various applications, including endoprostheses like hip implants, internal medical devices, and transcutaneous prostheses such as osseointegrated limb prosthetics for upper and lower extremities.

Preparation of carboxymethylcellulose / ZnO / chitosan composite hydrogel microbeads and its drug release behaviour

In this study, a novel carboxymethylcellulose / ZnO / chitosan (CMC / ZnO / Cs) hydrogel microbeads loaded with crosslinked porous starch / curcumin (CPS / Cur) were designed and prepared to improve the encapsulation efficiency of curcumin for drug delivery to specific sites. It was found that the total pore volume of crosslinked porous starch (CPS) was increased by 1150 % when compared to the native starch (NS), and the adsorption ratio of curcumin by CPS was enhanced by 27 % when compared to NS. Secondly, the swelling ratio of composite hydrogel microbeads was within 25 % in an acidic environment at pH 1.2, and the swelling ratio of hydrogel microbeads sharply increased to 320 % ~ 370 % at pH 6.8 and 7.4. In addition, the results of in vitro simulated release experiments showed that the released amount of hydrogel microbeads loaded with NS/Cur and CPS/Cur in SGF were within 7 % in simulated gastric fluid (SGF). The highest released amount of curcumin was 65.26 % for hydrogel beads loaded with CPS/Cur, which was 26 % lower than that of hydrogel microbeads loaded with Cur in simulated intestinal fluid (SIF). In simulated colonic fluid (SCF), the released amount of hydrogel microbeads loaded with CPS/Cur and Cur were 73.96 % and 91.69 %, respectively. In conclusion, pH-sensitive drug delivery system with good drug stability and bioavailability were successfully prepared with carboxymethylcellulose / ZnO / chitosan bead, suitable targeting drug delivery to the small intestine.

Fabrication of hydrogel microspheres via microfluidics using inverse electron demand Diels-Alder click chemistry-based tetrazine-norbornene for drug delivery and cell encapsulation applications

Microfluidic on-chip production of polymeric hydrogel microspheres (MPs) can be designed for the loading of different biologically active cargos and living cells. Among different gelation strategies, ionically crosslinked microspheres generally show limited mechanical properties, meanwhile covalently crosslinked microspheres often require the use of crosslinking agents or initiators with limited biocompatibility. Inverse electron demand Diels Alder (iEDDA) click chemistry is a promising covalent crosslinking method with fast kinetics, high chemoselectivity, high efficiency and no cross-reactivity. Herein, in situ gellable iEDDA-crosslinked polymeric hydrogel microspheres are developed via water-in-oil emulsification (W/O) glass microfluidics. The microspheres are composed of two polyethylene glycol precursors modified with either tetrazine or norbornene as functional moieties. Using a single co-flow glass microfluidic platform, homogenous MPs of sizes 200-600 μm are developed and crosslinked within 2 minutes. The rheological properties of iEDDA crosslinked bulk hydrogels are maintained with a low swelling degree and a slow degradation behaviour under physiological conditions. Moreover, a high-protein loading capacity can be achieved, and the encapsulation of mammalian cells is possible. Overall, this work provides the possibility of developing microfluidics-produced iEDDA-crosslinked MPs as a potential drug vehicle and cell encapsulation system in the biomedical field.

Self-cross-linked starch/chitosan hydrogel as a biocompatible vehicle for controlled release of drug

A facile one-pot approach was adopted to prepare a polysaccharide-based hydrogel of oxidized starch (OS)-chitosan. The synthetic monomer-free, eco-friendly hydrogel was prepared in an aqueous solution and employed for controlled drug release application. The starch was first oxidized under mild conditions to prepare its bialdehydic derivative. Subsequently, the amino group-containing a modified polysaccharide, "chitosan" was introduced on the backbone of OS via a dynamic Schiff-base reaction. The bio-based hydrogel was obtained via a one-pot in-situ reaction, where functionalized starch acts as a macro-cross-linker that contributes structural stability and integrity to the hydrogel. The introduction of chitosan contributes stimuli-responsive properties and thus pH-sensitive swelling behavior was obtained. The hydrogel showed its potential as a pH-dependent controlled drug release system and a maximum of 29 h sustained release period was observed for ampicillin sodium salt drug. In vitro studies confirmed that the prepared drug-loaded hydrogels showed excellent antibacterial ability. Most importantly, the hydrogel could find potential use in the biomedical field due to its facile reaction conditions, biocompatibility along with the controlled releasing ability of the encapsulated drug.

Progress in the application of sustained-release drug microspheres in tissue engineering

Sustained-release drug-loaded microspheres provide a long-acting sustained release, with targeted and other effects. There are many types of sustained-release drug microspheres and various preparation methods, and they are easy to operate. For these reasons, they have attracted widespread interest and are widely used in tissue engineering and other fields. In this paper, we provide a systematic review of the application of sustained-release drug microspheres in tissue engineering. First, we introduce this new type of drug delivery system (sustained-release drug carriers), describe the types of sustained-release drug microspheres, and summarize the characteristics of different microspheres. Second, we summarize the preparation methods of sustained-release drug microspheres and summarize the materials required for preparing microspheres. Third, various applications of sustained-release drug microspheres in tissue engineering are summarized. Finally, we summarize the shortcomings and discuss future prospects in the development of sustained-release drug microspheres. The purpose of this paper was to provide a further systematic understanding of the application of sustained-release drug microspheres in tissue engineering for the personnel engaged in related fields and to provide inspiration and new ideas for studies in related fields.

ROS-generating, pH-responsive and highly tunable reduced graphene oxide-embedded microbeads showing intrinsic anticancer properties and multi-drug co-delivery capacity for combination cancer therapy

The development of effective carriers enabling combination cancer therapy is of practical importance due to its potential to enhance the effectiveness of cancer treatment. However, most of the reported carriers are monofunctional in nature. The carriers that can be applied to concomitantly mediate multiple treatment modalities are highly deficient. This study fills this gap by reporting the design and fabrication of ROS-generating carbohydrate-based pH-responsive beads with intrinsic anticancer therapy and multidrug co-delivery capacity for combination cancer therapy. Sodium alginate (SA) microspheres and reduced graphene oxide (rGO)-embedded chitosan (CS) beads are developed via emulsion-templated ionic gelation for a combination therapy involving co-delivery of curcumin (CUR) and 5-fluororacil (5-FU). Drug-encapsulated microbeads are characterized by FTIR, DSC, TGA, XRD, and SEM. 5-FU and CUR-encapsulated microbeads are subjected to in vitro drug release studies at pH 6.8 and 1.2 at 37 °C. Various release kinetic parameters are evaluated. The results show that the Korsmeyer-Peppas model and non-Fickian release kinetics are best suited. The microspheres and microbeads are found to effectively act against MCF7 cells and show intrinsic anticancer capacity. These results indicate the promising performance of our beads in mediating combination drug therapy to improve the effectiveness of cancer treatment.

Deciphering the Molecular Mechanism of Water Interaction with Gelatin Methacryloyl Hydrogels: Role of Ionic Strength, pH, Drug Loading and Hydrogel Network Characteristics

Water plays a primary role in the functionality of biomedical polymers such as hydrogels. The state of water, defined as bound, intermediate, or free, and its molecular organization within hydrogels is an important factor governing biocompatibility and hemocompatibility. Here, we present a systematic study of water states in gelatin methacryloyl (GelMA) hydrogels designed for drug delivery and tissue engineering applications. We demonstrate that increasing ionic strength of the swelling media correlated with the proportion of non-freezable bound water. We attribute this to the capability of ions to create ion–dipole bonds with both the polymer and water, thereby reinforcing the first layer of polymer hydration. Both pH and ionic strength impacted the mesh size, having potential implications for drug delivery applications. The mechanical properties of GelMA hydrogels were largely unaffected by variations in ionic strength or pH. Loading of cefazolin, a small polar antibiotic molecule, led to a dose-dependent increase of non-freezable bound water, attributed to the drug’s capacity to form hydrogen bonds with water, which helped recruit water molecules in the hydrogels’ first hydration layer. This work enables a deeper understanding of water states and molecular arrangement at the hydrogel–polymer interface and how environmental cues influence them.

Immunostimulatory effect of chitosan and quaternary chitosan: A review of potential vaccine adjuvants

Vaccines have always been the most effective preventive treatment. Advancements in the field of vaccine is inseparable from adjuvants. Adjuvants are substances added to vaccines to enhance immunogenicity and induce a stronger immune response. Chitosan fascinated considerable attention as vaccine adjuvant due to its unique physicochemical and biological properties. Many studies have shown that chitosan and its derivatives can effectively activate antigen-presenting cells and induce cytokine stimulation to produce an effective immune response and promote the balance of Th1/Th2 response. Among many derivatives, the quaternized chitosan performs better. This review presents the main factors affecting the adjuvant performance of chitosan and quaternized chitosan firstly. Then, we introduced not only the immune response they may cause, but also their metabolic research in detail. Furthermore, their future prospects are forecasted. Overall, chitosan and quaternized chitosan are both promising adjuvant materials, and quaternized chitosan shows greater potential.

Microfluidic Fabrication of Structure-Controlled Chitosan Microcapsules via Interfacial Cross-Linking of Droplet Templates

In this work, a simple and flexible method for the fabrication of chitosan microcapsules with controllable structures and functions via the interfacial cross-linking reaction of the water-in-oil (W/O) emulsion templates is developed. The interfacial cross-linking reactions of chitosan and terephthalaldehyde (TPA) in W/O emulsion templates are comprehensively studied. The interfacial cross-linking reactions of the droplet templates in both batchwise and continuous conditions are studied. A poly(dimethylsiloxane) (PDMS) droplet-capture microfluidic chip is fabricated to investigate the interfacial reaction in continuous conditions online. In this study, the size and shell thickness of the microcapsules are affected by the preparation condition, such as the template size, emulsifier concentration, TPA concentration, and cross-linking time. Moreover, the size and shell thickness changes of chitosan microcapsules prepared in continuous conditions are much faster than those prepared in batchwise conditions. By regulating the preparation parameters, the microcapsules with controllable structures are fabricated in both batchwise and continuous conditions. The drug release behaviors of the microcapsules with controllable structures are studied. Furthermore, by adding magnetic nanoparticles to the aqueous solution, magnetic-responsive microcapsules are fabricated easily. This work provides valuable guidance for the controllable fabrication of chitosan microcapsules with designed structures and functions via single emulsion templates.

Impact of albumin corona on mucoadhesion and antimicrobial activity of carvacrol loaded chitosan nano-delivery systems under simulated gastro-intestinal conditions

Emerging antibiotic resistance in pathogens has posed considerable challenges to explore and examine the natural antimicrobials (NAMs). Due to the labile nature of NAMs, nano-delivery systems (NDS) are required to protect them from physiological degradation and allow controlled delivery to the targeted site of infection. In this study, corona modified NDS were developed using bovine serum albumin (BSA) on a chitosan core (CS) for sustained delivery of carvacrol (CAR), a natural antimicrobial agent, in the intestine. The optimal nano-formulations of the core (CS-NDS) and corona modified (BSA-CS-NDS) systems were fabricated with an average diameter of 52.4 ± 10.4 nm and 202.6 ± 6 nm, respectively. A shift in zeta-potential (ZP) from positive (+21 ± 3.6 mV) to negative values (-18 ± 2.6 mV) confirmed the electrostatic deposition of BSA corona on CS core. Under the influence of various simulated gastrointestinal conditions, BSA corona provided extra stability to NDS (ZP -38.5 mV), by ensuring delayed release and limited degradation in the gastric conditions. Mucoadhesive studies with quartz crystal microbalance with dissipation (QCM-D) revealed that BSA corona reduced the mucoadhesion of NDS at gastric pH, which enabled the effective delivery of CAR to the intestinal phase for successful eradication of Salmonella enterica.

Hydrogels as Drug Delivery Systems: A Review of Current Characterization and Evaluation Techniques

Owing to their tunable properties, controllable degradation, and ability to protect labile drugs, hydrogels are increasingly investigated as local drug delivery systems. However, a lack of standardized methodologies used to characterize and evaluate drug release poses significant difficulties when comparing findings from different investigations, preventing an accurate assessment of systems. Here, we review the commonly used analytical techniques for drug detection and quantification from hydrogel delivery systems. The experimental conditions of drug release in saline solutions and their impact are discussed, along with the main mathematical and statistical approaches to characterize drug release profiles. We also review methods to determine drug diffusion coefficients and in vitro and in vivo models used to assess drug release and efficacy with the goal to provide guidelines and harmonized practices when investigating novel hydrogel drug delivery systems.

Preparation of internally-crosslinked alginate microspheres: Optimization of process parameters and study of pH-responsive behaviors

In this study, the effects of various parameters of the water-in-oil emulsification/internal gelation method on the properties of calcium-alginate microparticles were evaluated and optimized. Results showed that the spherical-shaped microparticles with the highest circularity and high production yield can be produced by alginate solution with a concentration of 2 wt.%, calcium carbonate/alginate ratio of 10/1 (w/w), water/oil volume ratio of 1/20, emulsifier concentration of 5 % (v/v), and emulsification speed of 1000 rpm. Two model drugs including simvastatin lactone and simvastatin β-hydroxyacid were loaded into the microspheres with promising encapsulation efficiencies of 73 % and 69 %, respectively. The microspheres showed a pH-responsive swelling behavior with a percentage of 10.60 %, 352.65 %, 690.03 %, and 1211.46 % at the pH values of 2.0, 4.5, 7.4, and 8.5, respectively. The microspheres showed an increasing trend of release rate in direct proportion to pH. These findings would be useful for therapeutic applications which need pH-responsive drug carriers.

Modulation of Entrapment Efficiency and In Vitro Release Properties of BSA-Loaded Chitosan Microparticles Cross-Linked with Citric Acid as a Potential Protein-Drug Delivery System

Microparticles, aimed for oral protein and peptide drug delivery, were prepared via emulsion cross-linking using citric acid as cross-linker and polyglycerol polyricinoleate as surfactant. A comparative study of the interaction between chitosan and citric acid and its effect on the resulting microparticle properties was performed using different chitosan-to-cross-linker mass ratios and pH-values during fabrication of the microparticles. Non-cross-linked and cross-linked microparticles were studied in terms of size (4-12 μm), zeta potential (-15.7 to 12.8 mV), erosion (39.7-75.6%), a model protein encapsulation efficiency (bovine serum albumin) (6.8-27.6%), and loading capacity (10.4-40%). Fourier transform infrared spectroscopy and X-ray diffraction confirmed the ionic interaction between the protonated amine groups of chitosan and the carboxylate ions of the cross-linking agent. Scanning electron microscopy revealed that the non-cross-linked microparticles had an uneven shape with wrinkled surfaces, while the cross-linked formulations were spherical in shape with smooth surfaces. On the basis of these data, the role of the surfactant and microparticle structure on the release mechanism was proposed. Control of the microparticle shape and release mechanisms is expected to be crucial in developing carriers for the controlled delivery of proteins and peptides.

Effects of piceatannol on the structure and activities of bovine serum albumin: A multi-spectral and molecular modeling studies

Piceatannol (PIC) displays a wide spectrum of biological activities, such as antioxidation, antibacterial activity and anti-inflammation, but the biochemical and molecular mechanism is not fully understood. In this study, the interaction of PIC with bovine serum albumin (BSA) was studied by fluorescence spectroscopy, ultraviolet-visible absorption spectroscopy, circular dichroism spectroscopy and molecular simulation. The effects of PIC on BSA non-enzymatic glycosylation, fibrillation, thermal stability, and structure information were also studied. The results showed that the formation of PIC-BSA complex by mainly hydrogen-bonding forces resulted in the conformational changes of protein. PIC inhibited the formation of β-sheets structures of BSA. BSA still maintained the esterase-like good activity in the presence of PIC. In addition, PIC significantly reduced the degree of BSA glycosylation. These results provided a basis for the molecular interaction between PIC and protein, and suggested the potential effect of PIC in preventing the progression of diabetes mellitus.

Preparation of pH-Responsive Alginate-Chitosan Microspheres for L-Valine Loading and Their Effects on the A40926 Production

The glycopeptide A40926 biosynthesized by Nonomuraea gerenzanensis is a precursor of the second generation glycopeptide antibiotic dalbavancin. The skeleton of this glycopeptide consists of seven amino acids and is biosynthesized by the NRPS gene module. L-valine, a branched amino acid, is also a significant precursor for A40926 production. This study details the use of pH-responsive alginate-chitosan microspheres loaded with L-valine prepared by internal emulsification gelation. The effects of process and formulation variables on microsphere size, loading capacity, and encapsulation efficiency were investigated. Then, effects on A40926 production by the pH-responsive microspheres were evaluated in a 10-L fermenter. Results demonstrated that use of the pH-responsive microspheres could improve A40926 yield from 465 to 602 mg L^-1 in a 10-L scale fermenter.

Microenvironmental pH-modified Amisulpride-Labrasol matrix tablets: development, optimization and in vivo pharmacokinetic study

Amisulpride (AMS) is atypical antipsychotic with a weak basic nature (pKa 9.37), which results in low solubility in the high pH of the intestine. It is also recognized as a substrate of P-glycoprotein efflux pump. Both factors lead to its low oral bioavailability (48%). The daily dose of AMS is between 200 and 1200 mg to be taken in divided doses which compromise patient compliance. Therefore, controlled release formulation of AMS is of clinical significance. AMS was formulated into matrix tablets containing Labrasol, P-glycoprotein efflux inhibitor, and a penetration enhancer, using direct compression technique. The tablets were prepared according to 2¹·4¹ factorial design using two polymers, namely, HPMC and Carbopol 934 at four concentrations (20%, 30%, 40%, 50%). Percentage AMS released after 2 h (Q_2hr%) and 8 h (Q_8hr%) were chosen as dependent variables. Two acidic pH modifiers (fumaric acid and tartaric acid) at two levels (15% and 30%) were incorporated in the tablet according to 2² factorial design. All formulae with acidic pH modifier had similarity factor (f₂) ≥ 50 proving the pH independent release of AMS. The pharmacokinetic study in rabbits revealed 30% enhancement of the oral absorption AMS imparted by the pH-modified matrix tablet containing Labrasol. Graphical abstract.

Synthesis of polyacrylonitrile nanoflowers and their controlled pH-sensitive drug release behavior

A novel controlled drug release system based on pH sensitive polyacrylonitrile (PAN) nanoflowers in different kinds of solvents was successfully prepared with azobisisobutyronitrile (AIBN) as the initiator and without any emulsifier or stabilizer by a one step static polymerization method. The composition and structure of the PAN nanoflowers were analyzed by FTIR, XRD, SEM, TEM, and laser particle size analysis. The polymer particles consisted of a number of lamellae, with a sheet thickness of about 10 nm, and were similar to the shape of flowers with a particle diameter of about 350 nm. The mechanism of the polymerization reaction and the formation were studied. Moreover, the effects of monomer ratio, initiator concentration, reaction time, dispersion medium and co-monomer on the morphology and particle size of the nanoflowers were also discussed. A relatively large specific surface area was formed during the formation of the nanoflowers, which favored drug adsorption. The results of the in vitro experiments revealed that PAN(TBP) nanoflowers, containing BSA in buffer solution of pH 7.4, demonstrated good sustained-release and the cumulative release rate was about 83% after 260 h. The results also showed that the sustained-release from the PAN(TBP) nanoflowers best fitted the Riger-Peppas model. This study indicated that PAN(TBP) nanoflowers provided a theoretical base for the development of carriers for sustainable drug-release.

The schematic preparation of a new kind of pH-sensitive PAN nanoflower and its potential application for UC therapy. PAN (TBP) nanoflowers at pH 7.4 showed good sustained-release (t_83% = 260 h), which best fitted the Riger–Peppas model.

Micelles modified with a chitosan-derived homing peptide for targeted intracellular delivery of ginsenoside compound K to liver cancer cells

Ginsenoside compound K (CK), a major metabolite of protopanaxadiol ginsenosides, exhibits significant anticancer activities against various cancer cells. However, CK has poor water solubility and low bioavailability, which have limited its application. In this study, A54 peptide was utilized to fabricate CK-loaded micelles (APD-CK) for liver targeting, using deoxycholic acid-O-carboxymethyl chitosan as the vehicle. The average particle size of APD-CK micelles was about 171.4 nm by dynamic light scattering in the hydrated state and their morphology were spherical with good dispersion. An in vitro release assay indicated pH-responsive and sustained release behavior through a mechanism of non-Fickian diffusion. Moreover, the in vitro cytotoxicity of the APD-CK micelles against HepG2 and Huh-7 cells was significantly stronger than that of CK up to 20 μg/mL. Enhanced cellular uptake of micelles in both cell types was established using confocal fluorescence scanning microscopy and flow cytometry. In addition, western blot analysis revealed that APD-CK micelles could promote the protein expression levels of caspase-3, caspase-9, and poly (ADP-ribose) polymerase. Therefore, APD-CK micelles are a potential vehicle for delivering hydrophobic drugs in liver cancer therapy, enhancing drug targeting and anticancer activity.

Chitosan, hydroxypropyltrimethyl ammonium chloride chitosan and sulfated chitosan nanoparticles as adjuvants for inactivated Newcastle disease vaccine

Chitosan (CS) and its water-soluble derivatives, hydroxypropyltrimethyl ammonium chloride chitosan (HACC) and sulfated chitosan (SCS), were used as adjuvants of inactivated Newcastle disease (ND) vaccine. First, NDV-loaded and blank CS, HACC/CS and SCS nanoparticles were prepared. The particle sizes were respectively 343.43 ± 4.12, 320.03 ± 0.84, 156.2 ± 9.29 nm and the zeta potentials were respectively +19.67 ± 0.58, +18.3 ± 0.5, -17.8 ± 2.65 mV under the optimal conditions. Then chickens were immunized with nanoparticles or commercial inactivated oil emulsion vaccine. After immunization, the humoral immunity levels of the chickens were evaluated. The cellular immunity levels were determined by the quantification of cytokines, lymphocyte proliferation assay, the percentages of CD4⁺ and CD8⁺ T lymphocytes. Finally, the chickens were challenged with highly virulent virus. The results demonstrated that the humoral immunity levels in NDV-loaded CS and HACC/CS nanoparticles groups were lower than commercial vaccine but the cellular immunity levels are better. Moreover, the prevention effects of NDV-loaded CS and HACC/CS nanoparticles against highly virulent NDV are comparable to commercial vaccine. Our study provides the basis of developing HACC and CS as effective vaccine adjuvants.

Preparation of Chitosan Poly(methacrylate) Composites for Adsorption of Bromocresol Green

In the present study, chitosan poly(methacrylate) composites were prepared and applied for adsorption of bromocresol green from aqueous solutions. The synthesized composites were characterized with scanning electron microscopy, Fourier transform infrared spectroscopy, and thermogravimetric analysis. The bromocresol green removal by the developed adsorbent was investigated, and the effects of experimental parameters, including sample pH and adsorption time, were also examined. Furthermore, the adsorption characteristics of the synthesized adsorbent, including kinetics, adsorption isotherms, and thermodynamics, were comprehensively studied. The adsorption isotherm was well described by the Freundlich model, and the maximum adsorption capacity was 39.84 μg mg^-1 by shaking for 40 min at pH 2.0. Bromocresol green adsorption kinetics followed a pseudo-second-order kinetic model, indicating that adsorption was the rate-limiting step. Thermodynamic parameters and the negative values of Gibbs free energy change (ΔG°) showed that adsorption was a spontaneous process. The positive values of entropy change (ΔS°) implied that the adsorption of bromocresol green on chitosan poly(methacrylate) composites was an increasing random process. In addition, enthalpy change (ΔH°) values were positive, suggesting that the adsorption of bromocresol green was endothermic. The adsorption percentage of bromocresol green with chitosan poly(methacrylate) composites remained above 97% after three times of recycling test.

Design and synthesis of a calcium modified quaternized chitosan hollow sphere for efficient adsorption of SDBS

In this study, a new pleated hollow sphere material (CS@Ca@CTA) was prepared by mixing chitosan (CS) and calcium chloride (CaCl₂) in acetic acid solutions followed by crosslinking with glutaraldehyde (GA), and quaternized using (3-chloro-2 hydroxypropyl) trimethylammonium chloride (CTA). The natural biopolymer chitosan (CS) was used to prepare an environmentally friendly adsorbent material which can efficiently adsorb sodium dodecylbenzene sulfonate (SDBS). The adsorption of SDBS on CS@Ca@CTA can be efficiently improved by CTA at different pH values and Ca can promote the precipitation. The adsorption process of SDBS is as follows. First, SDBS can be adsorbed by electrostatic attraction and Cl^- of CTA is used to ion exchange DBS^- of SDBS. Then DBS^- can bind stably with the Ca²⁺ in a bidentate form. Furthermore, CS contains NH₂ and OH groups, which can provide enormous vacant active sites to adsorb SDBS, and a pleated surface have an ability to capture SDBS. The results indicated that the saturated adsorption capacity of CS@Ca@CTA up to 2300 mg g^-1 at pH 3.0 within 240 min. Additionally, adsorption kinetics, isotherm and thermodynamic parameters were discussed. The aim of this article is to present CS@Ca@CTA, which has a great effect on adsorbing the SDBS.

Molecular characterization of the effects of Ganoderma Lucidum polysaccharides on the structure and activity of bovine serum albumin

The investigation about polysaccharides-protein system is attributed to numerous very important applications for pharmaceutical, food, chemical and other industries. In the present work, multi-spectral methods and molecular docking were used to analyze the molecular interactions of polysaccharides from Ganoderma Lucidum (GLP) with bovine serum albumin (BSA). The nonenzymatic glucosylation, fibrillation, thermal stability, and structure information of GLP-BSA system were also studied. The results showed that the formation of GLP-BSA complex by mainly hydrogen-bonding forces resulted in the conformational changes of protein. GLP acted as a stabilizer to increase the thermal stability of BSA solution having a novel and more stable conformational state during the thermal denaturation process. 8-anilino-1-naphthalenesulfonic acid (ANS) fluorescence spectral results suggested that there exist some intermediate state which has low binding ability with ANS in the presence of GLP. The presence of GLP caused a decrease in the formation of beta sheet structures with a lower rate. The fluorescence spectra of BSA glycosylated by GLP confirmed the formation of covalent bonds between BSA and GLP through the Maillard reaction which was also confirmed by using thermogravimetric (TGA) and Fourier transform infrared (FTIR) analysis. In addition, BSA still maintains the esterase-like good activity in the presence of GLP. These results provide a basis for screening the molecular interactions of polysaccharides with protein from the perspective of important food active ingredients.

Fabrication of Quaternized Chitosan Nanoparticles Using Tripolyphosphate/Genipin Dual Cross-Linkers as a Protein Delivery System

Various amounts of 2-((acryloyloxy)ethyl)trimethylammonium chloride were grafted onto chitosan (CS) via redox polymerization method to obtain water-soluble quaternized CS (QCS). The QCS nanoparticles loaded with bovine serum albumin (BSA) were then produced by ionic gelation with tripolyphosphate (TPP) and further covalently cross-linked with genipin. The formation of QCS nanoparticles was optimized as a function of monomer grafting yield, QCS/TPP weight ratio, and QCS/genipin weight ratio by Box-Behnken design and response surface methodology. The results showed that QCS nanoparticles prepared with a grafting yield of 50%, QCS/TPP weight ratio of 7.67, and QCS/genipin weight ratio of 60 had a particle size of 193.68 ± 44.92 nm, polydispersity of 0.232, zeta potential of +23.97 mV and BSA encapsulation efficiency of 46.37 ± 2.89%, which were close to the predicted values from mathematical models. In vitro drug release studies at pH 1.2 and pH 7.4 exhibited that the release rate of BSA was significantly decreased and the release period was significantly prolonged after QCS nanoparticles cross-linking with genipin. Therefore, QCS nanoparticles cross-linked with TPP/genipin dual cross-linkers may be a promising protein drug carrier for a prolonged and sustained delivery.