Dye sorption and swelling of poly(vinyl alcohol) hydrogels in Congo red aqueous solution

Navigating the future: Microfluidics charting new routes in drug delivery

Microfluidics has emerged as a transformative force in the field of drug delivery, offering innovative avenues to produce a diverse range of nano drug delivery systems. Thanks to its precise manipulation of small fluid volumes and its exceptional command over the physicochemical characteristics of nanoparticles, this technology is notably able to enhance the pharmacokinetics of drugs. It has initiated a revolutionary phase in the domain of drug delivery, presenting a multitude of compelling advantages when it comes to developing nanocarriers tailored for the delivery of poorly soluble medications. These advantages represent a substantial departure from conventional drug delivery methodologies, marking a paradigm shift in pharmaceutical research and development. Furthermore, microfluidic platformsmay be strategically devised to facilitate targeted drug delivery with the objective of enhancing the localized bioavailability of pharmaceutical substances. In this paper, we have comprehensively investigated a range of significant microfluidic techniques used in the production of nanoscale drug delivery systems. This comprehensive review can serve as a valuable reference and offer insightful guidance for the development and optimization of numerous microfluidics-fabricated nanocarriers.

A high-precision and wide-range pH monitoring system based on broadband cavity-enhanced absorption spectrum

A high-precision pH monitoring system over a wide pH range is introduced. The system comprises a cavity-enhancement module constructed by two high-reflectivity mirrors, a microfluidic pH sensing chip based on a binary-indicator membrane of Congo red and m-cresol purple, and a hyperspectral transmission module. This structure extends the effective absorption optical path of the sensing chip, significantly amplifying the spectral differences at various pH values. The spectrum of the transmitted light is recorded by a self-developed hyperspectral module and then converted to broadband cavity-enhanced absorption spectrum (BBCEAS) via the Beer-Lambert law. An artificial neural network (ANN) is employed to predict pH values of the solution. With such a design, this system exhibits a wide detecting range of 2 M [H+] - 2 M [OH-] (corresponding to pH -0.3-14.3) with a response time of about 120 s. The system can achieve a higher detection accuracy with root mean square error (RMSE) of 0.073, as compared to 0.137 without the cavity enhancement. The system also possesses good properties of repeatability, long-term stability, ion resistance, and organic corrosion resistance. These excellent properties make the proposed system a promising candidate technology for harsh environments, such as seawater acidification warning, chemical plant sewage monitoring, and biological sample detection.

Spectroscopic Characterization of Azo Dyes Aggregation Induced by DABCO-Based Ionene Polymers and Dye Removal Efficiency as a Function of Ionene Structure

The aggregation mode of three azo dyes, methyl orange (MO), ponceau SS (PSS), and direct blue 1 (DB1) induced by three 1,4-diazabicyclo[2.2.2]octane (DABCO)-based ionene polymers having different topologies (i.e., 1,2-ionene, 1,3-ionene, and 1,4-ionene) was investigated in this work. Metachromatic behavior of the dyes in the presence of ionenes, and the stability of the ionene/dye complex were discussed as a function of ionene structure. It was demonstrated that the association of the dye molecules with the ionenes and the metachromasy were strongly influenced by both the dye structure and the ionene topology. Thus, MO, having one -SO₃Na group per molecule, was almost stoichiometrically bound to all ionenes regardless of their topology, showing also a metachromatic effect. In sharp contrast, the interaction of PSS and DB1 molecules with ionenes was strongly dependent on the polymer topology. It was found that PSS having two -SO₃Na groups per molecule was preferentially bound onto both 1,2-ionene and 1,3-ionene, but DB1, having four -SO₃Na groups per molecule and a more complex structure, was efficiently bound only onto 1,2-ionene. The dye removal efficiency with each ionene was evaluated in batch mode taking into account the affinity of ionenes for azo dyes. The experimental isotherms of the dye sorption were fitted with four isotherm models, i.e., Langmuir, Freundlich, Sips, and Dubinin-Radushkevich. It was found that the best fitting of the experimental data was given by the Langmuir, Sips, and Dubinin-Radushkevich isotherm models. The maximum equilibrium sorption capacity, q_m, evaluated by the Langmuir model, at 35 °C, was as follows: 985.71 mg MO/g 1,3-ionene, 483.71 mg PSS/g 1,3-ionene, 1010.49 mg PSS/g 1,2-ionene, and 976.7 mg DB1/g 1,2-ionene. Kinetic study of the dye removal indicated chemisorption as the main mechanism of sorption.