Biomolecular transitions and lipid accumulation in green microalgae monitored by FTIR and Raman analysis

Fourier transform infrared (FTIR) and Raman spectroscopic techniques were employed to analyze the biomolecular transitions and lipid accumulation in three freshwater green microalgal species, Monoraphidium contortum (M. contortum), Pseudomuriella sp. and Chlamydomonas sp. during various phases of their growth. Biomolecular transitions and lipid [hydrocarbons, triacylglycerides (TAGs)] accumulation within the microalgal cells were identified using second derivatives of the FTIR absorption spectroscopy. Second derivative analysis normalized and resolved the original spectra and led to the identification of smaller, overlapping bands. Both relative and absolute content of lipids were determined using the integrated band area. M. contortum exhibited higher accumulation of lipids than the other two species. The integrated band area of the vibrations from saturated (SFA) and unsaturated lipids (UFA) enabled quantification of fatty acids. The percentage of SFA and UFA was determined using GC, FTIR and Raman spectroscopy. From the spectral data, the order of increasing concentration of SFA among the three microalgal species was M. contortum > Chlamydomonas sp. > Pseudomuriella sp. The spectral results on fatty acids were consistent with the separation of lipids by gas chromatography. The results emphasized the significance of FTIR and Raman spectroscopic methods in monitoring the biomolecular transitions and rapid quantification of lipids, without the need for extraction of lipids

Effect of pH on weakly acidic and basic model drugs and determination of their ex vivo transdermal permeation routes

ABSTRACT The aim of the present study was to investigate the effect of donor pH on the transdermal permeability of the model drugs across rat skin and also to determine the major route of transport of the drugs. Weakly acidic drugs (partition coefficient) ibuprofen (3.6), aceclofenac (3.9), glipizide (1.9) and weakly basic drugs olanzapine (3.6), telmisartan (6.0), and sildenafil citrate (1.9) were selected for the study. The ex vivo permeation studies of these drugs at different donor pH (pH - 1.2, 4, 5, 6.8, 7.4, and 8) using Franz diffusion cell (area, 7.54 cm2) has shown a pH-dependent permeability. Among these drugs the weakly acidic drugs has shown higher permeation rates compared to the weakly basic drugs. The permeability coefficient and the distribution coefficient of the weakly basic drugs increased on increasing the pH whereas the weakly acidic drugs showed an inverse relation. The weakly basic drugs also showed an increase in permeation with increase in the fraction of unionized species indicating dominance of transcellular route of permeation. With an exception of sildenafil citrate, a weakly basic salt form of the drug which showed a high permeation value at pH 7.4 where 57% of the drug was unionized, indicating the involvement of both paracellular and transcellular route in its permeation

Preparation and optimization of various parameters of enteric coated pellets using the Taguchi L9 orthogonal array design and their characterization

Duloxetine hydrochloride enteric coated pellets were formulated using fluidized bed. Three separate layers, the drug layer, the barrier layer, and the enteric layer, were coated onto the inert core pellets. The pellets were optimized with the acid resistance and drug release in simulated intestinal fluid as the process parameters, using the Taguchi L9 orthogonal array. Various other properties, such as surface morphology, bulk and tapped density, Hausner's ratio, hardness, friability, yield of pellets, moisture content, and particle size distribution, were also studied in the optimized pellets. The concentration of the enteric polymer played a vital role in acid resistance, while the type of enteric polymer affected the drug release in simulated intestinal fluid. In both cases, it was determined that binder polymer concentration was not affected much. The comparisons between the optimized pellets and a market formulation yielded f1 and f2 values within a range of 4–5 and 60–65, respectively. Three month stability studies, conducted at accelerated conditions, showed the optimized pellets to be stable. Taguchi plays an important role in optimizing parameters, and optimization of duloxetine hydrochloride can be achieved with minimal trials

Design of a novel bilayered gastric mucoadhesive system for localized and unidirectional release of lamotrigine

AbstractLamotrigine is a BCS class II drug with pH dependent solubility. The bilayered gastric mucoadhesive tablets of lamotrigine were designed such that the drug and controlled release polymers were incorporated in the upper layer and the lower layer had the mucoadhesive polymers. The major ingredients selected for the upper layer were the drug and control release polymer (either HPMC K15M or polyox) while the lower MA layer predominantly comprised of Carbopol 974P. A 23 full factorial design was constructed for this study and the tablets were optimized for parameters like tablet size, shape, ex vivo mucoadhesive properties and unidirectional drug release. Oval tablets with an average size of 14mm diameter were set optimum. Maximum mucoadhesive bond strength of 79.3±0.91*103dyn/cm2 was achieved with carbopol when used in combination with a synergistic resin polymer. All the tested formulations presented a mucoadhesion time of greater than 12h. The incorporation of methacrylic polymers in the lower layer ensured unidirectional drug release from the bilayered tablets. The unidirectional drug release was confirmed after comparing the dissolution results of paddle method with those of a modified basket method. Model independent similarity and dissimilarity factor methods were used for the comparison of dissolution results. Controlled drug release profiles with zero order kinetics were obtained with polyox and HPMC K15M which reported t90% at 6th and 12th hours, respectively. The “n” value with polyox was 0.992 and that with HPMC K15M was 0.946 indicating an approximate case II transport. These two formulations showed the potential for oral administration of lamotrigine as bilayered gastric mucoadhesive tablets by yielding highest similarity factor values, 96.06 and 92.47, respectively, between the paddle and modified basket method dissolution release profiles apart from reporting the best tablet physical properties and maximum mucoadhesive strength

FORMULATION AND EVALUATION OF MEMBRANE-CONTROLLED TRANSDERMAL DRUG DELIVERY OF TOLTERODINE TARTARATE

Objective: The objective of the study was to formulate and evaluate membrane-controlled transdermal delivery system of Tolterodine tartrate (TT).Methods: TT membrane controlled transdermal patches were prepared by fabricating drug reservoir in a rate controlling membrane. Drug reservoir gel was prepared by using various polymers, rate controlling membrane is prepared by solvent casting method using Eudragit RL100 and RS100 in different ratios and was evaluated. The optimized formulations were fabricated and evaluated.Results: The membrane controlled transdermal patch of TT was optimized with HPMC K4 M gel (2.5%) and Eudragit RL100 & RS100(8:2) for rate controlling membrane. In-vitro, ex-vivo studies were conducted on rat abdominal skin and release at Q12 was 52.98±1.12μg/cm2 for F3 formulation over the control (8.85±0.74 μg/cm2). The flux was 3.574 μg/cm2/hr, lag time was 0.8 hrs, permeability coefficient was 1.068 cm/hr and permeation was enhanced by 2.33 fold for F3 formulation.Conclusions: Out of the prepared formulations the F3 transdermal patch was optimized having a steady state transdermal flux of 3.574 μg/cm2/hr, lag time of 0.8 hrs, enhancement ratio of 2.33 with permeability coefficient of 1.068 cm/hr and was subjected to ANOVA. ANOVA results showed significant difference between control and F3 in all skin permeation parameters. The optimized formulation (F3) exhibited controlled drug release profile with zero order kinetics and Fickian diffusion mechanism..Keywords: Membrane controlled transdermal system, Tolterodine Tartarate, Hydroxypropyl methylcellulose, Eudragit RL100, Eudragit RS100