Dynamic release of riboflavin from a starch-based semi IPN via partial enzymatic degradation: part II

Starch-based materials for drug delivery in the gastrointestinal tract-A review

Starch is a natural copolymer with unique physicochemical characteristics. Historically, it has been physically, chemically, or enzymatically modified to obtain ad-hoc functional properties for its use in different applications. In this context, the use of starch-based materials in drug delivery systems (DDSs) has gained great attention mainly because it is cheap, biodegradable, biocompatible, and renewable. This paper reviews the state of the art in starch-based materials design for their use in drug-controlled release with internal stimulus responsiveness; i.e., pH, temperature, colonic microbiota, or enzymes; specifically, those orally administered for its release in the gastrointestinal tract (GIT). Physical-chemical principles in the design of these materials taking into account their response to a particular stimulus are discussed. The relationship between the type of DDSs structure, starch modification routes, and the corresponding drug release profiles are systematically analyzed. Furthermore, the challenges and prospects of starch-based materials for their use in stimulus-responsive DDSs are also debated.

Thermoplastic starch/bentonite clay nanocomposite reinforced with vitamin B2: Physicochemical characteristics and release behavior

This study presents the development and characterization of a nanocomposite material, consisting of thermoplastic starch (TPS) reinforced with bentonite clay (BC) and encapsulated with vitamin B₂ (VB). The research is motivated by the potential of TPS as a renewable and biodegradable substitute for petroleum-based materials in the biopolymer industry. The effects of VB on the physicochemical properties of TPS/BC films, including mechanical and thermal properties, water uptake, and weight loss in water, were investigated. In addition, the surface morphology and chemical composition of the TPS samples were analyzed using high-resolution SEM microscopy and EDS, providing insight into the structure-property relationship of the nanocomposites. The results showed that the addition of VB significantly increased the tensile strength and Young's modulus of TPS/BC films, with the highest values observed for nanocomposites containing 5 php of VB and 3 php of BC. Furthermore, the release of VB was controlled by the BC content, with higher BC content leading to lower VB release. These findings demonstrate the potential of TPS/BC/VB nanocomposites as environmentally friendly materials with improved mechanical properties and controlled release of VB, which can have significant applications in the biopolymer industry.

Exploration of Zero-Valent Iron Stabilized Calcium–Silicate–Alginate Beads’ Catalytic Activity and Stability for Perchlorate Degradation

Perchlorate contamination in groundwater poses a serious threat to human health, owing to its interference with thyroid function. The high solubility and poor adsorption of perchlorate ions make perchlorate degradation a necessary technology in groundwater contaminant removal. Here, we demonstrate the perchlorate degradation by employing nano zero-valent iron (nZVI) embedded in biocompatible silica alginate hybrid beads fabricated using calcium chloride (1 wt%) as a crosslinker. The concentration of precursors (sodium alginate, sodium silicate) for bead formation was standardized by evaluating the thermal stability of beads prepared at different sodium silicate and alginate concentrations. Thermal degradation of silica alginate hybrid samples showed a stepwise weight loss during the thermal sweep, indicating different types of reactions that occur during the degradation process. The formation of the silica alginate hybrid structure was confirmed by FT-IR spectroscopy. Scanning electron microscopy (SEM) data revealed the surface morphology of silica alginate hybrid changes by varying sodium silicate and alginate concentrations. nZVI-loaded alginate–silicate polymer bead (nZVI-ASB) exhibited excellent perchlorate degradation efficiency by degrading 20 ppm of perchlorate within 4 h. Our study also showed the perchlorate degradation efficiency of nZVI-ASB is maximum at neutral pH conditions.

Nanoparticles based on phenylalanine ethyl ester-alginate conjugate as vitamin B2 delivery system

Phenylalanine ethyl ester (PAE)-alginate (Alg) conjugate (PAE-Alg, PEA) was synthesized and formation of an amide bond between PAE and Alg was confirmed by Fourier transformed-infrared and (1)H nuclear magnetic resonance spectroscopy. The degree of PAE substitution was 3.5-4.7 (PAE group per hundred sugar residues of Alg) which was determined by elemental analysis. The critical aggregation concentration values determined for PEA conjugates PEA1, PEA2, and PEA3 were 0.20, 0.12, and 0.10 mg/ml, respectively. The particle size of PEA nanoparticles (PEA-NPs) decreased from 425 nm to 226 nm with the increasing degree of PAE substitution. Vitamin B2 (VB2), as a model nutrient, was encapsulated into the nanoparticles. The drug-loading content increased with increasing degree of PAE substitution. The maximum VB2 loading capacity and loading efficiency of PEA3 nanoparticles were 3.53 ± 0.03% and 91.48 ± 0.80%, respectively. The in vitro release behavior of VB2 from the PEA-NPs showed a biphasic release profile with an initial burst release of about 40-50% of VB2 in the first 10 h followed by a steady and continuous release phase for the following 50 h in PBS, pH 7.4. The human colorectal carcinoma cell line was used to investigate the cytotoxicity of PEA-NPs. Our results showed that various concentrations of nanoparticles did not cause significant cytotoxicity against cell lines at normal concentrations.

Natural alginate biopolymer montmorillonite clay composites for vitamin B2 delivery

This work describes the in vitro release of a small drug, riboflavin, from novel calcium and barium crosslinked alginate–montmorillonite composite beads via oral route. Effect of crosslinking cation, concentration of montmorillonite and media on encapsulation efficiencies, and release profiles of riboflavin were studied. Beads were characterized using gravimetric swelling ability study, Fourier transform infrared spectroscopy, and scanning electron microscopy. Results indicate that addition of montmorillonite increases the encapsulation efficiencies and slows down the release rates significantly.

The release dynamics of model drugs from the psyllium and N-hydroxymethylacrylamide based hydrogels

In order to utilize the psyllium husk, a medicinally important natural polysaccharide, for developing the novel hydrogels for the controlled drug delivery device, we have prepared psyllium and N-hydroxymethylacrylamide based polymeric networks by using N,N'-methylenebisacrylamide (N,N'-MBAAm) as crosslinker. The polymeric networks thus formed were characterized with scanning electron micrography (SEM), FTIR and thermogravimetric analysis (TGA) techniques to study various structural aspects of the networks and also with the swelling response of the polymeric networks as a function of time, temperature, pH and [NaCl]. Equilibrium swelling has been observed to depend on both structural aspects of the polymers and environmental factors. Maximum P(s) 748.3 was observed at 13.0 x 10(-3)mol/L of [N,N'-MBAAm] in 0.5M NaOH solution. The release dynamics of model drugs (salicylic acid and tetracycline hydrochloride) from hydrogels has also been discussed, for the evaluation of the release mechanism and diffusion coefficients. The effect of pH on the release pattern of tetracycline has been studied by varying the pH of the release medium. In release medium of pH 7.4 buffer the release pattern of tetracycline drastically changes to the extent that mechanism of drug diffusion shifted from non-Fickian diffusion to Fickian diffusion. It has been observed that diffusion exponent "n" have 0.71, 0.67 and 0.52 values and gel characteristic constant 'k' have 1.552 x 10(-2), 2.291 x 10(-2) and 5.309 x 10(-2) values in distilled water, pH 2.2 buffer and pH 7.4 buffer, respectively, for tetracycline release. In solution of pH 7.4 buffer, the rate of polymer chain relaxation was more as compare to the rate of drug diffusion from these hydrogels and it follows Fick's law of diffusion. The value of the initial diffusion coefficient for the release of tetracycline hydrochloride was higher than the value of late time diffusion coefficient in each release medium indicating that in the start, the diffusion of drug from the polymeric matrix was fast as compare to the latter stages.