Fickian Diffusion Research Articles

Programmable Release of Chemotherapeutics from Ferrocene-Based Injectable Hydrogels Slows Melanoma Growth.

Hydrogel-based injectable drug delivery systems provide temporally and spatially controlled drug release with reduced adverse effects on healthy tissues. Therefore, they represent a promising therapeutic option for unresectable solid tumor entities. In this study, a peptide-starPEG/hyaluronic acid-based physical hydrogel is modified with ferrocene to provide a programmable drug release orchestrated by matrix-drug interaction and local reactive oxygen species (ROS). The injectable ROS-responsive hydrogel (hiROSponse) exhibits adequate biocompatibility and biodegradability, which are important for clinical applications. HiROSponse is loaded with the two cytostatic drugs (hiROSponsedox/ptx) doxorubicin (dox) and paclitaxel (ptx). Dox is a hydrophilic compound and its release is mainly controlled by Fickian diffusion, while the hydrophobic interactions between ptx and ferrocene can control its release and thus be regulated by the oxidation of ferrocene to the more hydrophilic state of ferrocenium. In a syngeneic malignant melanoma-bearing mouse model, hiROSponsedox/ptx slows tumor growth without causing adverse side effects and doubles the relative survival probability. Programmable release is further demonstrated in a tumor model with a low physiological ROS level, where dox release, low dose local irradiation, and the resulting ROS-triggered ptx release lead to tumor growth inhibition and increased survival.

Thermo-responsive composite nanoparticles based on hydroxybutyl chitosan oligosaccharide: Fabrication, stimulus release and cancer therapy

Designing thermo-responsive nanocarriers based on biopolymers is fascinating and challenging for cancer therapy. In this study, thermo-responsive composite nanoparticles (CNPs) were prepared using hydroxybutyl chitosan oligosaccharide (HBCOS) and sodium caseinate (SC) via electrostatic interactions and covalent crosslinking. The temperature-responsive behaviors of CNPs were induced by the breakage of hydrogen bonds and the shrinkage of chains in nanoparticles. The CNPs exhibited concentration-independent thermo-responsive behavior, non-adsorption aggregation, and non-hemolysis, suggesting excellent stability and thermo-sensitivity. The initial release rate and final amount of DOX released from CNPs at 42 °C were higher than that at 37 °C, showing a thermo-responsive release, which was also more prominent at lower pH. The release of DOX from CNPs followed first order kinetics based on Fickian diffusion. In vitro cytotoxicity assays confirmed the thermo-responsive antitumor activity of DOX-loaded CNPs as the HT-29 cell viability incubated with DOX-loaded CNPs at 42 °C was significantly lower than that at 37 °C. Cellular uptake experiments proved that DOX-loaded CNPs accumulated in the cytoplasm after being endocytosed and promoted DOX release by increasing environment temperature. This study generated stable thermo-sensitive CNPs based on biopolymers, which can be used as potential nanocarriers for the controlled release of anticancer drugs for cancer therapy.

Morphological, thermal and mechanical properties of wheat‐straw reinforced copper nanocomposite

AbstractThe work summarizes an innovative nanocomposite including synthesized copper nanoparticle (CuNP) impregnated wheat straw (WS) (the agronomic waste from an wheat plant) reinforced unsaturated polyester resin has been established. The addition of nanoparticles (NPs) increased the antifungal properties (~11%), durability (~9%), and strength (~39%) of the composites. Therefore, these nanoparticles have been synthesized from a copper chloride dihydrate precursor and they have been impregnated into wheat straw via cationization. This copper‐impregnated wheat straw (CuIWS) was formulated and employed to create a strong and long‐lasting nanocomposite with unsaturated polyester resin. Their morphological, mechanical, chemical, biodegradability (BD), and thermal properties were estimated and relationships were explicated systematically. Particularly, the tensile strength of polyester resin, crude and treated WS (cationized and copper‐impregnated) composites were 11.70, 14.20, 20.92, and 22.34 N/mm2 respectively. Therefore the reinforcement capability for crude, cationized and copper‐impregnated WS composites increased by ~22%, 75%, and 92% respectively. The residual ash was just about 16.23%, 12.04% and 6.56% for copper impregnated wheat straw composite (CuIWSC), Cationized wheat straw composite (CWSC) and untreated wheat straw composite (UTWSC) respectively point to the existence of ~4.1% Cu incorporated into the wheat straw which holds up the energy dispersive x‐ray (EDX) spectra of ~4.2% copper content. Thermogravimetric analysis (TGA) indicates that the nanocomposites are stable up to 325°C. These nanocomposites also show superlative crystallinity compared to other ones. Water uptake capacity followed typical Fickian diffusion law. The developed nanocomposites might be suitable for automobile and aircraft parts, furniture, and other indoor to outdoor applications.Highlights TS of the composites increased by increasing the WS filling up to 15%. The crystallinity increased after the addition of nanoparticles. The typical water uptake properties followed the Fickian diffusion rule. Incorporation of nanoparticles increased 11% antifungal properties. The developed nanocomposites are used for inside and outside applications.

PH-responsive chitosan-mediated spherical mesoporous silica microspheres for high loading and controlled delivery of 5-Fluorouracil

The objective of this study is to develop a drug carrier to overcome the inherent drawbacks of 5-Fluorouracil (5-Fu), including low bioavailability, short half-life, and systemic toxicity. In the present work, mesoporous silica nanoparticles (MSNs) capped by chitosan (CS) to encapsulate 5-Fu (5-Fu MSNs/CS) were fabricated by the sol-gel process, ultrasonic impregnation, and emulsion cross-linking. The 5-Fu MSNs/CS microspheres exhibit pH-responsive drug release and remarkable drug encapsulation capacity, as well as perfect sphericity, high specific surface area (680.62 cm2/g), and uniform particle size (2.64 ± 0.05 μm). The drug-loading content and encapsulation efficiency are 14.12 ± 0.53 % and 82.21 ± 2.13 %, respectively. The cumulative release of 5-Fu from MSNs/CS microspheres is fast and sustained at pH 5.0 (89.56 ± 0.97 %) compared to that at pH 7.4 (57.88 ± 0.91 %) in 96 h, and it is Fickian diffusion controlled. In conclusion, the MSNs/CS microspheres prepared in this study could be potential carriers for 5-Fu delivery.

Pharmaceutical Properties of the Phloretin-4,4'-Bipyridine Cocrystal: Structure Analysis, Drug Release Profile, and Antioxidant Activity Research.

To improve the water solubility of phloretin, we synthesized the Phl-4B cocrystal using the solvent evaporation method. Various analytical techniques including powder X-ray diffraction (PXRD), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), Fourier transform infrared (FTIR), 1HNMR, and single-crystal X-ray diffraction (SCXRD) were employed to evaluate the crystal thermodynamics and structure. The results of PXRD and SCXRD showed that it was a new cocrystal crystallized in the P-1 space group of the triclinic system. Thermal analysis confirmed the purity of the Phl-4B cocrystal. The equilibrium solubility of the Phl-4B cocrystal in pH 1.2 was improved. In vitro simulated digestion experiments indicated that the release of the Phl-4B cocrystal followed Fick diffusion. The stability activity of phloretin after pharmaceutical cocrystallization was improved. The antioxidant of the Phl-4B cocrystal was better than that of pure Phl.

Kinetic study of in vitro release of curcumin from chitosan biopolymer and the evaluation of biological efficacy

Sustained release of curcumin from the polymeric carrier system chitosan, a natural biopolymer material derived from chitin originated from natural shrimp shell waste, was studied. Six kinetic models, zero order, first order, Korsmeyer–Peppas (KP), Peppas – Sahlin (PS), Higuchi, and Hixson–Crowell, were applied to study the drug release kinetics. The release mechanism of the drug from the curcumin-chitosan composite was evaluated by changing the pH, ionic strength of the release media, and drug concentration. KP and PS models were selected among the studied models to investigate the drug release mechanism from the chitosan biopolymer based on the R2 values (R2 > 0.99). The model constants m in the PS model and n in the KP model stand for the case II relaxation and Fickian diffusion contribution, respectively. The n being < 0.43 in the KP model suggests that the Fickian diffusion governs the drug release. Furthermore, there is a noticeable difference between the values obtained for model parameters m and n in the PS and KP models, indicating that Case II relaxation and Fickian diffusion play crucial roles in the curcumin release mechanism from chitosan. Polymer relaxation has been proven to play a predominant role in releasing curcumin from the composite at lower ionic strengths and higher pH values. Anti-inflammatory activity was tested using the egg-albumin denaturation assay, and the diphenyl-2-picrylhydrazyl assay was carried out to determine the antioxidant activity of the composite. The composite material showed IC50 values of 0.29 mg/ mL and 1.08 mg/ mL for anti-inflammatory and anti-oxidant activities, respectively. The drug composite has shown antibacterial activity against Pseudomonas aeruginosa, Klebsiella pneumoniae, and Staphylococcus aureus, which are highly effective against S.aureus. The resulting inhibition zones for S.aureus were 13.34 ± 0.34 mm, 16.34 ± 0.60 mm, and 13.34 ± 0.73 mm for 5, 10, and 20 mg/ml concentrations, respectively. The drug composite’s minimum inhibitory concentration/ minimum bactericidal concentration ratio for S.aureus, K. pneumoniae, and P.aeruginosa was greater than 4, suggesting that they cause bacteriostatic effects.

Facile preparation of a pH-sensitive biocompatible nanocarrier based on magnetic layered double hydroxides/Cu MOFs-chitosan crosslinked к-carrageenan for controlled doxorubicin delivery to breast cancer cells

Recently, the biocompatibility of hydrogel nanoparticles has gained considerable research attention in the field of drug delivery. In this regard, we design a pH-controlled nanocarrier based on magnetic layered double hydroxides/copper metal-organic framework-chitosan crosslinked к-carrageenan hydrogel nanoparticles (LDH-Fe3O4/Cu MOF-DOX-CS@CAR) for targeted release from DOX to breast cancer cells. FT-IR, EDX, XRD, FE-SEM, VSM, and Zeta potential investigated the chemical structure of hydrogel nanoparticles. The encapsulation efficiency and drug loading capacity of the DOX were obtained to be 96.1 % and 9.6 %, respectively. The cumulative release of DOX from LDH-Fe3O4/Cu MOF-DOX-CS@CAR at pH 5.5 and 7.4 after 72 h was 60.3 % and 22.6 %, respectively. These in vitro release results confirmed the controlled release and pH-response behavior of hydrogel nanoparticles. Also, the mechanism of DOX release from LDH-Fe3O4/Cu MOF-DOX-CS@CAR hydrogel nanoparticles showed that the Korsmeyer-Peppas model with Fickian diffusion is the best-fitting model for describing the release behavior of DOX from hydrogel nanoparticles. The cellular cytotoxicity and DAPI tests of the prepared LDH and LDH-Fe3O4/Cu MOF toward L929 non-cancerous cells and MCF-7 breast cancer cells confirm its relative biocompatibility and safety. Whereas, LDH-Fe3O4/Cu MOF-DOX-CS@CAR hydrogel nanoparticles toward MCF-7 breast cancer cells had higher cytotoxicity effects due to the targeted and controlled release of DOX to MCF-7 cells. The in vitro DPPH, hemolysis assay, colloidal stability, and enzymatic degradation proved the excellent antioxidant activity (71.81 %), blood compatibility (less than 5 %), better stability, and biodegradation behavior of hydrogel nanoparticles. On these findings, the present study suggests the potential of the prepared LDH-Fe3O4/Cu MOF-DOX-CS@CAR hydrogel nanoparticles as a pH-controlled drug delivery system for cancer treatment and various biomedical uses.

Diffusion-induced stress amplification in phase-transition materials for electrodes of lithium-ion batteries

This work sheds the light on the stress amplification in active material particles of electrodes caused by the localized lithium concentration inhomogeneity due to phase transitions. This is a significant issue usually neglected in the literature, as generally the ideal Fickian diffusion model is used to describe the lithium diffusion, which particularly fails when dealing with phase change materials, resulting in the underestimation of the stress. In turn, this results in the underestimation of the fracture behavior of the electrode and the battery degradation, ultimately.To overcome these limitations, this work proposes a mechanical-transport model where the lithium transport is modeled according to the non-ideal solution theory with an equivalent diffusion coefficient depending on the potential of the host material vs Li/Li+. The results show that the proposed model correctly describes the concentration distribution within the particle of phase-change materials (graphite is chosen as a case study), in agreement with the existent experimental measurements. The differences with respect to the traditional Fickian diffusion model is substantial as the stress is up to 85% higher with the proposed model and the concentration distribution can capture the inhomogeneity caused by phase transitions.

Electrospun film polyvinyl alcohol/chitosan loaded with cinnamon essential oil and inhibitory effects on polyphenol oxidase and dominant spoilage bacteria from Pacific white shrimp

Pacific white shrimp (Litopenaeus vannamei) is prone to melanosis and spoilage during refrigeration. To develop an active packaging material with inhibitory effects on polyphenol oxidase (PPO) (related with melanosis) and specific spoilage organisms of refrigerated spoilage Litopenaeus vannamei (Lv-SSOs), one degradable polyvinyl alcohol-chitosan (PVA-CS) fibrous mats encapsulating cinnamon essential oil (CEO) were fabricated by electrospinning. Compared to PVA-CS, the transparency, tensile strength and water contract angle of CEO-loaded electrospun film (CEO/PVA-CS) were all significant increased. CEO molecules uniformly dispersed between PVA-CS fiber bundles without any visible gaps under scanning electron microscopy observation. Fourier transform infrared spectroscopy and X-ray diffraction analyses revealed that CEO successfully embedded into PVA-CS matrix through inter-molecular forces, thus improving the compact of CEO/PVA-CS. In simulate food systems (4 °C and 25 °C), the release patterns of CEO from CEO/PVA-CS fit well to Higuchi and Rigter-Peppas models, and could be explained by the Fickian diffusion mechanism. At refrigeration (4 °C), CEO/PVA-CS had 57.52 ± 3.33% inhibition rate on PPO, extracted from the cephalothorax of Litopenaeus vannamei, after 7 h of interaction. Moreover, CEO/PVA-CS effectively inhibited Lv-SSOs growth at 4 °C. Therefore, the electrospun film of CEO/PVA-CS should have potential application prospects in delaying melanosis and spoilage of refrigerated shrimp.

Development and characterization of curcumin nanosuspension-embedded genipin-crosslinked chitosan/polyvinylpyrrolidone hydrogel patch for effective wound healing

This study investigated the development of a genipin-crosslinked chitosan (CS)-based polyvinylpyrrolidone (PVP) hydrogel containing curcumin nanosuspensions (Cur-NSs) to promote wound healing in an excisional wound model. Cur-NSs were prepared, and a simplex centroid mixture design was employed to optimize hydrogel properties for high water absorption, degree of crosslinking, and sufficient toughness. The in vivo wound healing effect was tested in Wistar rats. The optimized hydrogel consisted of a 70:30 ratio of CS:PVP, crosslinked with a 2 % w/w genipin solution. It exhibited high swelling capability (486 %) while maintaining solidity, robustness, and durability. Incorporating 5 % w/w Cur-NSs resulted in a more compact structure, although with a reduction in swelling properties. The release kinetics of Cur from the hydrogel followed the Korsmeyer-Peppas Fickian diffusion model. In vitro biocompatibility studies demonstrated that the hydrogel was non-toxic to skin fibroblast cells. The in vivo experiment revealed a desirable wound healing rate with over 80 % recovery by day 7. Cur-NSs likely aided wound healing by reducing the inflammatory response and stimulating fibroblast proliferation. Additionally, the CS-based hydrogel provided a moist wound environment with hydration and gas transfer, further accelerating wound closure. These findings suggest that the Cur-NS-embedded hydrogel shows promise as a wound dressing material.

Quasi-static bending analysis of composite laminated cylindrical panels under hygrothermal conditions

The combined effects of temperature and humidity, termed hygrothermal, are included in the deformation analysis of laminated composite cylindrical panels based on first-order shear deformation theory (FSDT). The panel is under transverse mechanical load, and both steady-state and transient hygrothermal loads are considered. The problem is solved using the minimum potential energy theorem for different boundary conditions. The moisture profile through the thickness is obtained by analytical solution of Fick diffusion equation. The dependency of moisture diffusion coefficient on temperature is considered and the material temperature is assumed to be the same as the environmental temperature. Using a semi-analytical approach, displacement field of the panel subjected to evaluated profile of moisture in a specific time and thermo-mechanical loads is obtained. The accuracy and validation of the present solution are demonstrated by solving numerical examples and comparing them with the results available in the literature. Furthermore, new results are presented and effects of various important parameters such as panel geometry, edge boundary conditions, lamination layups and imposed moisture conditions on the deformation of the composite cylindrical panel are studied. Solved examples demonstrate that higher length-to-arc and radius-to-thickness ratios result in increased deflection and amplify the influence of mechanical load compared to hygrothermal effects on the overall deformation of the panel. In most case studies, the hygroscopic deformation observed at one-tenth of the saturation time exceeded half of the deformation observed after the saturation time, which shows the importance of transient hygroscopic analysis.

Development of High-Efficiency Fertilizer by Hydrogels Obtained from Cassava Starch and Citric Acid for Slow Release of Ammonium and Potassium.

Fertilizers with enhanced efficiency or high-efficiency fertilizers increase the nutrient availability, minimize losses, and reduce costs, thereby increasing crop yields and food production while mitigating environmental impacts. This research evaluates the synthesis of biodegradable hydrogels from cassava starch and citric acid for agrochemical applications. Hydrogels were synthesized using water as the solvent and applied for the controlled release of macronutrients (N and K). Four concentrations of nutrient-containing salts were tested (0.5 to 10.0% w/w). Materials were analyzed using ATR-FTIR spectroscopy and swelling studies. The presence of nutrients reduced both the crosslinking efficacy and the water absorption capacity, with the latter dropping from 183.4 ± 0.6% to 117.9 ± 3.7% and 157.4 ± 25.0% for hydrogels loaded with NH4Cl and KCl, respectively. The cumulative release of K and N from the hydrogel was monitored for 144 h and examined using kinetics models, revealing that the releases follow Fickian's diffusion and anomalous diffusion, respectively. Additionally, the material was formed using cassava with peel previously milled to reduce the production costs, and its potential for nutrient-controlled delivery was evaluated, with the finding that this hydrogel decreases the release rate of nitrogen. The results suggest that these biomaterials may have promising applications in the agrochemical industry in the making of high-efficiency fertilizers.

The process of sucrose crystallization in the supersaturated solution

Crystallization processes of the solid phase in supersaturated solutions of products of plant origin are used in processing technologies. The theory of diffusion (molecular) mass transfer of the target substance has become widespread when solving problems of technology improvement. The driving force of this process is the difference in the concentration of the solid phase in the solution towards the crystallization center, where the concentration of the solid phase is reduced. During the analytical and quantitative study of the process of solid phase deposition in the crystallization center, Fick's diffusion laws have been used. The influence of solution temperature, concentration of the solid phase, its geometry and dispersed composition on the course of this process have been considered. Based on a diffusion model of the process of crystal formation of sucrose in a vacuum apparatus, a numerical analysis of factors in sugar production technology not covered in the literature has been presented. The problem of quantitative analysis of the process of sucrose crystallization in the working volume of a vacuum apparatus for the production of sugar and other products of plant origin of high commercial standards requires further in-depth study.

Nanorod Diffusion near the Solid-Liquid Interface with Varied Wall Nonuniformity.

The complex diffusion behaviors of rod-shaped nanoparticles near the solid-liquid interface are closely related to various biological processes and technological applications. Despite recent advancements in understanding the diffusion dynamics of nanoparticles near some specific solid-liquid interfaces, systematical studies to tune the interfacial interaction or fabricating nonuniform wall to see their effects on the nanorod (NR) diffusion are still lacking. This work utilized molecular dynamics simulations to investigate the rotational and translational diffusion dynamics of a single NR near the solid-liquid interface. We constructed a patterned wall featuring adjustable nonuniformity, which was accomplished by modifying the interaction between NR and the wall, noting that the resulting nonuniformity limits both the translational and rotational diffusion of NR, evident from decreases in diffusion coefficients and exponents. By trajectory analysis, we categorized the diffusion modes of NRs near the patterned wall with varied nonuniformities into three types: Fickian diffusion, desorption-mediated flight, and in-plane diffusion. Furthermore, energy analysis based on the adsorption-desorption mechanism has demonstrated that the three diffusion states are driven by interactions between the NR and the wall, which are primarily influenced by rotational diffusion. These results could significantly deepen the understanding of anisotropic nanoparticle interfacial diffusion and would provide new insights into the transport mechanisms of nanoparticles within confined environments.

A grey-box model with neural ordinary differential equations for the slow voltage dynamics of lithium-ion batteries: Application to single-cell experiments

Lithium-ion batteries exhibit a complex, nonlinear and dynamic voltage behaviour. Modelling their slow dynamics is a challenge due to the multiple potential causes involved. We present here a neural equivalent circuit model for lithium-ion batteries including slow voltage dynamics. The model uses an equivalent circuit with voltage source, series resistor, and diffusion element. The series resistance is parameterized using neural networks. The diffusion element is based on a discretized form of Fickian diffusion, parameterized using a neural network and learnable parameters. It is flexible to represent not only Warburg behaviour, but also resistor-capacitor-type dynamics. Mathematically, the resulting model is given by a differential–algebraic equation system combining ordinary and neural differential equations. Therefore, the model combines concepts of both physical theory (white-box model) and artificial intelligence (black-box model) to a combined framework (grey-box model). We apply this approach to a lithium iron phosphate based lithium-ion battery cell. The experimental voltage behaviour during constant-current cycles as well as the dynamics during pulse tests are well reproduced by the model. Only at very high and very low states of charge the simulation significantly deviates from experiments, which might result from insufficient training data in these regions.

A novel paraffin-based N/P controlled-release material for biostimulation of phenol biodegradation in groundwater

To address the problem of the weak natural restoration ability of oligotrophic groundwater environments, a novel N/P controlled-release material (CRM) for biostimulation, prepared by an improved method, was developed. CRMs can encapsulate N and P (N/P) salts for sustained release in aquifers. Paraffin-based CRMs can be used to control N/P release rates by adjusting the particle size of CRMs and the mass ratio of the paraffin. The developed CRMs had a more remarkable adaptability to groundwater than other materials. Specifically, 0.4-cm CRMs released N/P stably and efficiently over a wide temperature range (7–25 ℃), and the release properties of various CRMs were not affected by pH. The release of N/P followed Fickian diffusion, and a dissolution-diffusion model was established to elucidate the mechanism of the controlled release. In contrast to bare N/P, CRMs obviously enhanced the biodegradation rate of phenol and prolonged the effectiveness of supplying N/P. The degradation rate of phenol in the CRM system increased by 20.8 %. The different supply modes of N/P, CRMs and bare N/P, resulted in differences in salinity. Metagenomic analysis showed that this difference changed the proportion of various phenol-degrading genera and thus changed the abundance of genes associated with the phenol degradation pathway.

Design and evaluation of fluorescent chitosan-starch hydrogel for drug delivery and sensing applications

Composite bio-based hydrogels have been obtaining a significant attention in recent years as one of the most promising drug delivery systems. In the present study, the preparation of composite chitosan-starch hydrogel using maleic acid as a cross-linker was optimized with the help of response surface methodology. The synthesized hydrogel was fluorescent owing to clustering of large number of functional groups. Different analytical techniques, including XRD, FTIR, SEM, XPS, fluorescence and BET were utilized to characterize the prepared hydrogel. XRD analysis confirmed the formation of non-crystalline hydrogel with random arrangement of macromolecular chains. The composite hydrogel exhibited good swelling percentage with pH sensitivity, hemocompatibility and degradability. BET analysis confirmed that the variation in concentration of crosslinker significantly influences the pore volume of the hydrogel. The synthesized composite chitosan-starch hydrogel was utilized as a prospective candidate for controlling drug release. Cefixime as a model drug was loaded onto the synthesized hydrogel utilizing the swelling diffusion method. SEM micrographs showed uniform distribution of drug molecules in the drug loaded hydrogel. In vitro drug release experiments indicated the swelling dependent drug release behaviour of chitosan-starch hydrogel with higher drug release at pH 7.4 (93.08 %) compared to pH 1.2 (67.85 %). The composite chitosan-starch hydrogel was able to prolong and control the drug release up to 12 h. The drug release from the hydrogel followed Korsmeyer-Peppas and Makoid-Banakar model with Fickian diffusion mechanism. Further, the composite hydrogel displayed excitation dependent fluorescence emission with most intense blue emission band at 425 nm with an excitation wavelength of 350 nm. The inclusion of cefixime drug in the hydrogel matrix significantly reduced the fluorescence intensity; the decrease was linearly correlated to the concentration of the drug. Moreover, the fluorescence emission the chitosan-starch hydrogel was found to be dependent upon pH. The synthesized hydrogel is expected to be a potential candidate for controlled drug release as well as for fluorescent sensing applications.

Design and evaluation of oseltamivir phosphate dual-phase extended-release tablets for the treatment of influenza

In this study, once-daily extended-release tablets with dual-phase release of oseltamivir phosphate were developed for the treatment of influenza. The goal was to improve patient adherence and offer more therapeutic choices. The tablets were manufactured using wet granulation, bilayer tablet compression, and enteric membrane-controlled coating processes. Various polymers, such as hydroxypropyl methylcellulose (HPMC K100MCR, K15MCR, K4MCR, K100LV), enteric polymers (HPMC AS-LF, Eudragit L100-55) and membrane-controlled polymers (OPADRY® CA), were used either individually or in combination with other common excipients. The formulations include enteric-coated extended-release tablet (F1), hydrophilic matrix extended-release tablet (F2), semipermeable membrane-controlled release tablet (F3) and a combination extended-release tablet containing both enteric and hydrophilic matrix (F4). The in vitro drug release profile of each formulation was fitted to the first-order model, and the Ritger-Peppas model suggested that Fickian diffusion was the primary mechanism for drug release. Comparative bioequivalence studies with Tamiflu® (oseltamivir phosphate) capsules revealed that formulations F1, F2, and F3 did not achieve bioequivalence. However, under fed conditions, formulation F4 achieved bioequivalence with a relative bioavailability of 95.30% (90% CI, 88.83%-102.15%). This suggests that the formulation F4 tablet could potentially be a new treatment option for patients with influenza.

Dual-responsive, highly bacteriostatic and swellable chitosan-based hydrogels loaded with 5-fluorouracil for sustainable release

In this work, a dual-responsive hydrogel for sustainable release of drug was prepared using chitosan grafted with PBA as substrate to form semi-interpenetrating polymer networks (S-IPN) via free-radical crosslinking polymerization of acrylic acid in the presence of MBAA as a crosslinker and KPS as an initiator as well as Fe3+.ions introduced. The results from comprehensive characterization indicated that the as-prepared hydrogel possesses cavity structure with the pores of varying sizes, thus facilitating the accommodation of 5-fluorouracil as a model drug. In addition, the swelling behavior of the hydrogels in different pH buffers and glucose solutions was also investigated. As expected, the prepared hydrogels are pH and glucose responsive due to PAA and phenylboronic acid incorporated into the hydrogel, which enables the slow or sustainable release of drug. Moreover, the release processes were fitted with various kinetic models whereas the release was better described by Korsmeyer-Peppas model or the drug release is mainly governed by the release mechanism of the hydrogel is primarily driven by Fickian diffusion from a mechanical point of view. Hydrogel loaded with drug was found to have good antibacterial effects against E. coli and S. aureus, leading to the potential for various medical-related applications.

Investigation of delivery mechanism of curcumin loaded in a core of zein with a double-layer shell of chitosan and alginate

The pursuit of efficient drug delivery systems has led to innovative approaches such as matrix and core-shell structures. This study explores these systems with a focus on enhancing the delivery and stability of curcumin, a bioactive compound with therapeutic potential. Matrix systems using zein protein were fabricated through coaxial airflow extrusion with a vibration generator, while core-shell systems were produced using concentric nozzles. Double-layer reservoir systems were also formed by coating chitosan-shelled structures with an alginate solution. Encapsulation of curcumin within each system was confirmed through FTIR and optical microscope analysis, followed by efficiency evaluation, which was measured approximately 86.5 ± 0.7 % for the matrix systems and 90 ± 0.8 % for the core-shell systems. Moreover, the particle sizes of matrix systems were measured in the range of 2000–2100 mμ and the particle sizes of single-layer and double-layer reservoir systems were in the ranges of 1600–1700 mμ and 1500–1700 mμ, respectively. The study investigated the stability of curcumin in these systems under various environmental conditions, including exposure to light, heat, pH variations, ions, and storage. Results demonstrated that the presence of multiple layers significantly enhanced the drug's stability. Afterwards, swelling and drug release profiles were assessed in simulated gastric, intestinal, and colon fluids. The swelling of the matrix, single-layer and double-layer reservoir systems after 29 h were 127.4 %, 146.9 % and 144 %, respectively. The matrix system showed 68.7 % drug release after 29 h, whereas single-layer chitosan-shelled and double-layer chitosan/alginate-shelled reservoir systems released 51.8 % and 45.6 % of the drug, respectively. The release mechanism was explored using zero-order, Korsmeyer-Peppas, and Kopcha kinetic models. Comparative analysis of the experimental results and model fittings indicated a deviation from Fickian diffusion, with erosion becoming more pronounced with each additional layer. In conclusion, the system with a zein core and double-layer chitosan/alginate shell displayed effective drug release regulation and enhanced stability of curcumin, making it a promising candidate for efficient drug delivery.