Experimental Analysis and Neural Network Modeling of the Rheological Behavior of Xanthan Gum and Its Derivatives.

The main objective of this study was to create a mathematical tool that could be used with experimental data to predict the rheological flow behavior of functionalized xanthan gum according to the types of chemical groups grafted onto its backbone. Different rheological and physicochemical analyses were applied to assess six derivatives synthesized via the etherification of xanthan gum by hydrophobic benzylation with benzyl chloride and carboxymethylation with monochloroacetic acid at three (regent/polymer) ratios R equal to 2.4 and 6. Results from the FTIR study verified that xanthan gum had been modified. The degree of substitution (DS) values varying between 0.2 and 2.9 for carboxymethylxanthan gum derivatives were found to be higher than that of hydrophobically modified benzyl xanthan gum for which the DS ranged from 0.5 to 1. The molecular weights of all the derivatives were found to be less than that of xanthan gum for the two types of derivatives, decreasing further as the degree of substitution (DS) increased. However, the benzyl xanthan gum derivatives presented higher molecular weights varying between 1,373,146 (g/mol) and 1,262,227 (g/mol) than carboxymethylxanthan gum derivatives (1,326,722-1,015,544) (g/mol). A shear-thinning behavior was observed in the derivatives, and the derivatives' viscosity was found to decrease with increasing DS. The second objective of this research was to create an ANN model to predict one of the rheological properties (the apparent viscosity). The significance of the ANN model (R2 = 0.99998 and MSE = 5.95 × 10-3) was validated by comparing experimental results with the predicted ones. The results showed that the model was an efficient tool for predicting rheological flow behavior.

Formulation and Evaluation of Xanthan Gum Microspheres for the Sustained Release of Metformin Hydrochloride.

This work aimed to formulate xanthan gum microspheres for the encapsulation of metformin hydrochloride, according to the process of ionotropic gelation. The obtained microparticles, based on various fractions of xanthan gum (0.5-1.25), were subjected to different physico-chemical tests and a drug release study. Microspheres with an average size varying between 110.96 µm and 208.27 µm were obtained. Encapsulation efficiency reached 93.11% at a 1.25% biopolymer concentration. The swelling study showed a swelling rate reaching 29.8% in the gastric medium (pH 1.2) and 360% in the intestinal medium (pH 6.8). The drug release studies showed complete metformin hydrochloride release from the beads, especially those prepared from xanthan gum at the concentration of 1.25%, in intestinal medium at 90.00% after 6 h. However, limited and insignificant drug release was observed within the gastric medium (32.50%). The dissolution profiles showed sustained release kinetics.

Synthesis and physicochemical evaluation of octenylsuccinated kappa-carrageenan: Conventional versus microwave heating.

This research reported on the synthesis and the evaluation of new octenyl succinate (OS) kappa-carrageenan (KC) esterified derivatives (KC-OS). Two derivatives were synthesized using microwave (KC-OSMM) and conventional heating (KC-OSCM). The FT-IR and 1H NMR demonstrated the KC-OS esters formation with a higher degree of substitution for KC-OSMM (0.85) than KC-OSCM (0.62). The SEM testing showed the non-deteriorated morphology of KC after modification. The amphiphilic properties and surface activity of KC-OSs investigated by the conductivity method confirmed the formation of self-assembled aggregates beyond a critical aggregation concentration of 0.08% for KC-OSMM and 0.12% for KC-OSCM. Stable oil-in-water emulsions were formulated based on KC-OSs at the concentrations of 0.75% and 1%. Lower globule sizes were observed for KC-OSMM emulsions at 0.75% (12.30 µm) and 1% (08.86 µm), compared to KC-OSCM at 0.75% (32.75 µm) and 1% (19.6 µm). All results demonstrated that microwave synthesis resulted in obtaining novel derivatives with superior properties.

Synthesis, characterization and potential application of hydrophobically modified carrageenan derivatives as pharmaceutical excipients.

New amphiphilic derivatives of kappa-carrageenan (KC) were synthesized by hydrophobic modification with octyl chloride. Two different methods based on microwave and conventional heating were used. All KC derivatives (KCRs) were characterized by different techniques. The FT-IR and 1HNMR studies demonstrated that the octyl groups were effectively grafted onto KC backbone and confirmed that the derivative KCRMM, obtained by microwave heating, presented a higher degree of substitution (DS = 0.77) compared to KCRCM (0.45). The amphiphilic character investigation also revealed that KCRMM exhibited a lower critical aggregation concentration (CAC) value of 0.13% w/v than KCRCM (0.15%). Furthermore, KCRs greatly improved the stability of oil/water emulsions as the droplet size decreased with increasing DS. Unlike the conventional heating method, novel derivatives with a higher DS, greater amphiphilic character, and an improved emulsifying power were obtained by microwave-assisted synthesis. These derivatives could potentially be used in food, cosmetics, or as excipients in pharmaceutics.