DESIGN AND CHARACTERIZATION OF A BIOCOMPATIBLE PHYSICAL HYDROGEL BASED ON SCLEROGLUCAN FOR TOPICAL DRUG DELIVERY

Optimized scleroglucan production by Athelia rolfsii and in vitro Sclg-5-fluorouracil release investigations

Scleroglucan is a notable member of the β-glucan microbial polysaccharides with a long tradition of industrial and therapeutic use. The local strain, previously identified as Athelia rolfsii TEMG MH 236106 produced an appreciable amount of scleroglucan using glucose as a carbon source and yeast extract as a nitrogen source. Plackett-Burman design was employed to effectively screen critical medium composition, culture, and fermentation conditions. Athelia rolfsii TEMG MH 236106 produced the maximum amount of scleroglucan (18.12 g/L) with a 45.3 % glucose conversion. Out of the eleven variables, the most effective factors showing a high level of significance are as follows: glucose, yeast extract, citric acid, inoculum disc numbers, culture volume and incubation time. An update to maximize scleroglucan production in the central composite design for four parameters (glucose and yeast extract concentrations, disc number, medium volume and incubation time) with 31 runs was applied and the production of scleroglucan reached its maximum at 31.56 g/L with 78.9 % glucose conversion. Three models of Sclg-5-fluorouracil complexes have been employed to study in vitro drug release investigations. Hence, the Sclg-5-FU (5 and 10 mg/mL) models appeared to be the most suitable for drug administration due to their concentration and distribution within capsules.

Fabrication and Evaluation of Poly(2-hydroxyethyl methacrylate)/Eudragit L-100 Hydrogels with Fusidic Acid to Promote Eczema Treatment

In this study, hydrogels containing 2-hydroxyethyl methacrylate (HEMA), Eudragit L-100, and fusidic acid in different compositions were prepared with the confinement method by using ammonium persulfate (APS) as a chemical initiator and ethylene glycol dimethacrylate (EGDMA) as a cross-linker to determine the most suitable formulation for use in eczema treatment. Fusidic acid (FA)-confined pHEMA/Eudragit L-100 in synthesis of the hydrogel was used with the Taguchi method, and the optimum synthesis conditions were determined. The swelling percentages of the hydrogels were calculated in different pH environments and distilled water. Also, the cream formulations developed and contained in chitosan and HEMA-based polymers were synthesized. Viscosity and pH values changed between 30,000 and 100,000 cP and between 5 and 6 for different cream formulations with various conditions, respectively. Also, swelling percentages of hydrogels were between 20 and 40. Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) analyses were performed to characterize the hydrogel structure and the cream formulations. In addition, the stability of the formulations to 28 days and the changes in parameters such as appearance, centrifugation, pH, relative density, viscosity, spreading were evaluated, comparatively.

Polysaccharide-based hydrogels crosslink density equation: A rheological and LF-NMR study of polymer-polymer interactions

A simple relation between pendant groups of polymers in hydrogels is introduced to determine the crosslink density of (complex) hydrogel systems (mixtures of 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) modified nanocellulose, alginate, scleroglucan and Laponite in addition of crosslinking agents). Furthermore, the rheological properties and their great potential connection to design complex hydrogel systems with desired properties have been thoroughly investigated. Hydrogel structures governing internal friction and flow resistance were described by the predominant effect of ionic, hydrogen, and electrostatic interactions. The relationship between rheological properties and polymer-polymer interactions in the hydrogel network is explained and expressed in a new mathematical model for determining the crosslink density of (crosslinked) hydrogels based on single or mixture of polymer systems. In the end, the combined used of rheology and low field nuclear magnetic resonance spectroscopy (LF-NMR) for the characterization of hydrogel networks is developed.

Novel drug-loaded film forming patch based on gelatin and snail slime

Gelatin-based films enriched with snail slime are proposed as novel biodegradable and naturally bioadhesive patches for cutaneous drug delivery. Films (thickness range 163-248 μm) were stretchable and they adhered firmly onto the wetted skin, especially those with high amount (70% V/V) of snail slime extract. Fluconazole was selected as model drug and added to films containing the highest amount of snail slime. The presence of Fluconazole (4.53 ± 0.07% w/w) did not modify significantly the mechanical properties, the swelling degree and the bioadhesive performances of the films. Structural investigations demonstrated that the crystalline form III of the drug changed to the amorphous one, forming an amorphous solid dispersion. Moreover, snail slime prevented the drug recrystallization over time. In vitro permeation studies showed that film exhibited a cumulative drug concentration (over 60% in 24 h) similar to that of the control solution containing 20% w/V of ethanol. Fluconazole-loaded gelatin films proved to be effective towards clinical isolates of Candida spp. indicating that the drug maintained its remarkable antifungal activity once formulated into gelatin and snail slime-based films. In conclusion, snail slime, thanks to its peculiar composition, has proved to be responsible of optimal skin adhesion, film flexibility and of the formation of a supersaturating drug delivery system able to increase skin permeation.

Enhanced Loading Efficiency and Mucoadhesion Properties of Gellan Gum Thin Films by Complexation with Hydroxypropyl-β-Cyclodextrin

Polymeric oral thin films (OTFs) were prepared by the casting method, combining gellan gum (GG), a water-soluble polysaccharide, and glycerol (Gly) as a plasticizing agent. GG-Gly films were investigated as potential systems for buccal drug delivery using fluconazole (Class I of the Biopharmaceutical Classification System) as a model drug. At a low concentration of Gly drug precipitation occurred while, for higher concentrations of Gly, a significant deterioration of mucoadhesive and mechanical properties was observed. One possible way to overcome all these problems could be the addition of hydroxypropyl-β-cyclodextrin (HP-β-CD) to the GG-Gly formulation as a drug-precipitation inhibitor. In this work the effect of cyclodextrin addition on the mechanical, mucoadhesive, swelling and release properties of GG-Gly films was investigated. In-vitro drug release studies were carried out using the paddle type dissolution apparatus (USP II) and the millifluidic flow-through device (MFTD). A moving-boundary model for swelling dynamics and release in USP II is proposed to estimate the effective diffusivity of the solvent, HP-β-CD, fluconazole and complex fluconazole/HP-β-CD in the swelling film. Experimental results, supported by theoretical modeling, confirmed that gellan gum-low glycerol thin films including HP-β-CD represent a suitable formulation for fluconazole drug delivery. A sustained release was observed when GG-Gly film is loaded with a preformed complex fluconazole/HP-β-CD.

Gelation of the internal core of liposomes as a strategy for stabilization and modified drug delivery II. Theoretical analysis and modelling of in-vitro release experiments

PEG-DMA was incorporated in unilamellar liposomes. PEG-DMA crosslinking by photo-induced radical reaction transforms the liquid aqueous core of the liposome into a hydrogel. The molecular weight of PEG-DMA significantly influences both structural and release properties of these hybrid nanosystems, by affecting both membrane permeability and diffusional properties of the inner core. Release studies of 5-(6) carboxyfluorescein from Conventional Liposomes (CL) and Gel-in-Liposome (GiL) systems were carried out in a vertical Franz Diffusion Cell. A detailed transport model is proposed, aimed at describing the entire drug diffusive pathway from the vesicles' inner core, through the double-layer membrane, into the buffer solution in the donor chamber of the Franz Cell and from there to the receptor chamber, where withdrawals are performed to evaluate the released drug concentration. The model permits to give a quantitative estimate of the diffusional resistances offered by the inner core (liquid or gelled) and by the double-layer membrane for CLs and different GiLs systems. The theoretical analysis of experimental release data strongly supports the basic assumption that, by varying the molecular weight of PEG-DMA, a different arrangement of the polymer within the liposomal structure and a different interaction with the membrane occur. PEG₇₅₀-DMA decreases the transport resistance of the double layer membrane with respect to CLs, while PEG₄₀₀₀-DMA plays the opposite role. After gelation of the internal core, the diffusional resistance to drug transport inside GiLs becomes controlling, thus significantly slowing down drug release from these systems. Therefore, the combination of PEG-DMA with phospholipid vesicles appears an interesting strategy to develop sustained drug delivery systems.

Fmoc-diphenylalanine as a suitable building block for the preparation of hybrid materials and their potential applications

Due to its capability to self-assemble in self-supporting hydrogels (HG) under physiological conditions, Fmoc-FF is one of the most studied ultra-short peptide. The structural properties of the resulting hydrogel (mechanical rigidity, entanglement of the fibrillary network, and the thickness of the fibers) strictly depend on the experimental conditions used during the preparation. In the past few years, a broad range of applications in different fields, such as biomedical and industrial fields, have been proposed. However, the research on novel materials with enhanced mechanical properties, stability, and biocompatibility has brought about the development of novel Fmoc-FF-based hybrid systems, in which the ultra-short hydrogelator is combined with others entities such as polysaccharides, polymers, peptides, or organic molecules. The structural features and the potential applications of these novel hybrid materials, with particular attention to tissue engineering, drug delivery, and catalysis, are described here. The aim is to give the readers a tool to design new hybrid nanomaterials based on the Fmoc-FF dipeptide hydrogelator, with appropriate properties for specific applications.

Gellan Gum/Laponite Beads for the Modified Release of Drugs: Experimental and Modeling Study of Gastrointestinal Release

In this study, gellan gum (GG), a natural polysaccharide, was used to fabricate spherical porous beads suitable as sustained drug delivery systems for oral administration. GG was cross-linked with calcium ions to prepare polymeric beads. Rheological studies and preliminary experiments of beads preparation allowed to identify the GG and the CaCl2 concentrations suitable for obtaining stable and spherical particles. GG beads were formed, through ionotropic gelation technique, with and without the presence of the synthetic clay laponite. The resultant beads were analyzed for dimensions (before and after freeze-drying), morphological aspects and ability to swell in different media miming biological fluids, namely SGF (Simulated Gastric Fluid, HCl 0.1 M) and SIF (Simulated Intestinal Fluid, phosphate buffer, 0.044 M, pH 7.4). The swelling degree was lower in SGF than in SIF and further reduced in the presence of laponite. The GG and GG-layered silicate composite beads were loaded with two model drugs having different molecular weight, namely theophylline and cyanocobalamin (vitamin B12) and subjected to in-vitro release studies in SGF and SIF. The presence of laponite in the bead formulation increased the drug entrapment efficiency and slowed-down the release kinetics of both drugs in the gastric environment. A moving-boundary swelling model with "diffuse" glassy-rubbery interface was proposed in order to describe the swelling behavior of porous freeze-dried beads. Consistently with the swelling model adopted, two moving-boundary drug release models were developed to interpret release data from highly porous beads of different drugs: drug molecules, e.g., theophylline, that exhibit a typical Fickian behavior of release curves and drugs, such as vitamin B12, whose release curves are affected by the physical/chemical interaction of the drug with the polymer/clay complex. Theoretical results support the experimental observations, thus confirming that laponite may be an effective additive for fabricating sustained drug delivery systems.

An approach to enhanced stability: Formulation and characterization of Solanum lycopersicum derived lycopene based topical emulgel

Focus of the study was to design a novel and cost effective extraction technique for the lycopene from Lycopersicum esculentum L. fruit and to develop and characterize a stable emulgel formulation containing lycopene as an active ingredient as well as to design an analytical method to determine lycopene concentration in emulgel. Emulgel formulation was prepared and evaluated for its stability at different storage conditions, 8 °C, 25 °C, 40 °C, 40 °C + 75% relative humidity (RH) and 50 °C, for 6 months. Results were statistically analyzed using two way ANOVA, Post-Hoc test and paired sample t-test at 5% significance level. Designed extraction technique presented comparable yield, 154.83 mg/Kg of tomato fruit, with all recoveries in the range of 145-156 mg/Kg of tomato. "P-values" calculated for different levels of stability parameters were <0.05, except at 50 °C and time points of 60th day and later. Analytical method designed was having linear range of lycopene 1-10 µg/mL with limit of detection 0.11 µg/mL and limit of quantification 0.34 µg/mL. All inter-day and intra-day recoveries were in the range of 94-105% while in all measurements RSD % was ≤5.36. It can be concluded that the extraction technique was cost effective with comparable results and analytical method was simple, robust, specific and sensitive enough to be used for lycopene concentration determination in emulgel formulation. Furthermore, designed formulation was stable even at high temperature of 40 °C and RH 75%.

Antibacterial activity of PEO nanofibers incorporating polysaccharide from dandelion and its derivative

A water-soluble antibacterial polysaccharide from dandelions (PD) was chemically modified to obtain its carboxymethylated derivative (CPD). The degree of substitution of CPD was 0.455. Fourier transform infrared (FTIR) spectra analysis, zeta potential, particle size and rheological test verified the carboxymethylation of PD, accompanying with the change of physicochemical properties. Moreover, Listeria monocytogenes treated with 10 mg/mL PD and CPD achieved 1.96 and 3.29 log CFU/mL reduction in population, respectively. Subsequently, PD and CPD were incorporated into polyethylene oxide (PEO) nanofiber matrix to fabricate antimicrobial nanofibers. The prepared nanofibers were characterized by scanning electron microscope, atomic force microscope and FTIR. Finally, both PD/PEO and CPD/PEO nanofibers exhibited favourable antibacterial effect on L. monocytogenes, with an improved antibacterial activity of CPD/PEO nanofibers than PD/PEO nanofibers. In conclusion, this study demonstrated PD and CPD could be applied to the fabrication of antibacterial food packaging.