Microscopic and Spectroscopic Imaging and Thermal Analysis of Acrylates, Silicones and Active Pharmaceutical Ingredients in Adhesive Transdermal Patches

Techno-economic assessment of waste mandarin biochar as a green adsorbent for binary dye wastewater effluents of methylene blue and basic fuchsin: Lab- and large-scale investigations

Treating polluted wastewater effluents on a large-scale requires the development of high performance and cost-effective adsorbents. The recycling of waste mandarin peels, an environmentally friendly, and copiously available waste biomass into biochar (MRBC), has been approached. In the context of finding affordable and effective solutions for depollution of wastewater, MRBC was used for the adsorption of two dyes: methylene blue (MB) as well as basic fuchsin (BF) from their individual solutions and binary combinations. Batch adsorption studies were performed by employing the Box-Behnken (BB) design. The adsorption competency of dyes was analyzed to find the percentage removal (%R) and the adsorption capacity (qe, mg/g). The dependent parameters (qe and %R) were determined as a function of pH, dose of MRBC (AD), contact time (CT), and concentration of methylene blue [MB]/ basic fuchsin [BF]. Removal of 98.14% of MB and 83.18% of BF was successfully achieved. Equilibrium experiments depicted that Langmuir and Freundlich models suit adsorption of dyes. The maximum adsorption capacity (qmax) was 99.11 (MB) and 78.01 mg/g (BF), individually. However, when the dyes are combined, the qmax decreased to 57.09 and 68.52 mg/g for MB and BF, correspondingly. The cost of MRBC was estimated to be ∼ 4 USD/kg, while the overall cost of wastewater treatment was estimated to be 1.06 USD/m3/year.

The Impact of Liquid Components on Alteration of the Adhesion of Polyacrylate and Silicone Patches

Polyacrylates and polysiloxanes are polymers used in pressure-sensitive adhesive (PSA) patches. Liquid additives are co-solvents of the active substances or permeation enhancers, and their compatibility with the polymeric matrix and the effect on adhesive properties should be considered. The patches were prepared from commercial polyacrylates (three types of Duro-Tak®) and siloxanes (Bio-PSA® and Soft Skin Adhesive®). Propylene glycol, polyoxyethylene glycol, isopropyl myristate, triacetin, triethyl citrate and silicone oil were added (10% w/w). Formulations were evaluated microscopically and with a texture analyzer in terms of in vitro adhesiveness and hardness. Only silicone oil was compatible with the silicone matrices. The best compatibility of acrylic PSA was observed with triethyl citrate; one out of three Duro-Tak matrices was incompatible with every additive. In all compositions, the adhesiveness was impaired by the liquid additives. A significant drop in adhesiveness was noted after immersion of the patches in buffer and drying. The probe tack test was considered as the most useful for evaluation of the effect of the liquid additive on adhesiveness, but the results obtained with a spherical and cylindrical probe were contradictory. The structural changes caused by the additives were also demonstrated by a 90° peel test, considered as complementary to the tack test.

Design, Development, and Evaluation of Treprostinil Embedded Adhesive Transdermal Patch

Clinical application of treprostinil in pulmonary arterial hypertension is hampered by adverse effects caused by its high dosing frequency. The objective of this investigation was to Formulate an adhesive-type transdermal patch of treprostinil and evaluate it both in vitro and in vivo. A 3²-factorial design was utilized to optimize the selected independent variables (X₁: drug amount, X₂: enhancer concentration) on the response variables (Y₁: drug release, Y₂: transdermal flux). The optimized patch was evaluated for various pharmaceutical properties, skin irritation, and pharmacokinetics in rats. Optimization results signify considerable influence (p < 0.0001) of X₁ on both Y₁ and Y₂, as compared to X₂. The optimized patch possesses higher drug content (>95%), suitable surface morphology, and an absence of drug crystallization. FTIR analysis revealed compatibility of the drug with excipients, whereas DSC thermograms indicate that the drug exists as amorphous in the patch. The adhesive properties of the prepared patch confirm adequate adhesion and painless removal, while the skin irritation study confirms its safety. A steady drug release via Fickian diffusion and greater transdermal delivery (~23.26 µg/cm²/h) substantiate the potential of the optimized patch. Transdermal therapy resulted in higher treprostinil absorption (p < 0.0001) and relative bioavailability (237%) when compared to oral administration. Overall, the results indicate that the developed drug in the adhesive patch can effectively deliver treprostinil through the skin and could be a promising treatment option for pulmonary arterial hypertension.

Heat capacity of cytisine - the drug for smoking cessation

The characterization of cytisine (CYT) and its blends with poly(lactic acid) was performed using thermal analysis, elemental analysis, infrared spectroscopy, and powder X-ray diffractometry. The heat capacities, total enthalpy, and phase transitions of CYT were established from 1.8 to 448.15 K (-271.35 - 175 °C) by advanced thermal analysis. Data were obtained using a Quantum Design Physical Property Measurement System (PPMS) and a differential scanning calorimetry (DSC). The low-temperature heat capacity of the crystalline CYT in the range of 1.8 to 300 K (-271.35 - 26.86 °C) was measured by PPMS and fitted to a theoretical model in the low temperature region below 11 K (-262.15 °C), to orthogonal polynomials in the middle range 5 K < T < 60 K (-268.15 °C < t < -213.15 °C) and to the Debye and Einstein functions in the high range of temperature above 60 K (-213.15 °C). The liquid heat capacity was calculated based on the approximated linear regression data above the molten state of the experimental heat capacity of CYT obtained by the standard DSC measurements, and it was expressed as C_p^liquid = 0.0838T + 346.78 J·K^-1·mol^-1. The calculated heat capacity in the solid state was extended to a higher temperature and was used, together with liquid heat capacity, as the reference baselines for the advanced thermal analysis of CYT. The PPMS and DSC/TMDSC methods are complementary methods for thermal analysis of cytisine. The PPMS method allowed determination of the equilibrium heat capacity in the solid state, which together with the equilibrium heat capacity in the liquid state allowed to analyze of the experimental apparent heat capacity of cytisine obtained based on DSC. The melting temperature and the total heat of fusion of crystalline material were established as 431.8 K (158.65 °C) and 26.5 kJ·mol^-1, respectively. The solid and liquid heat capacities and transition parameters of CYT were applied to calculate total enthalpies for fully amorphous and crystalline states. Analyses of DSC and X-ray confirmed the presence of the solid-solid transition linking with not so far described a polymorphism phenomenon of CYT. Based on the thermogravimetric analysis the temperature of degradation of CYT was determined as 460.5 K (187.35 °C). Also, a preliminary thermal analysis of the blends of cytisine and poly(lactic acid) as a new candidate for drug delivery system was presented.