Determination of protonation state in molecular salt of minoxidil and 2,4-dihydroxybenzoic acid through a combined experimental and theoretical study: influence of proton transfer on biological activities

Cellulose nanocrystal-stabilized Pickering emulsion gels as vehicles for follicular delivery of minoxidil

Minoxidil (MXD) is the only topical over-the-counter medicine approved by the United States Food and Drug Administration for the treatment of androgenetic alopecia. For the purpose of targeting the delivery of MXD to dermal papilla in the hair follicle, MXD Pickering emulsion gels were fabricated based on the designability of deep eutectic solvent (DES) and the versatility of cellulose nanocrystal (CNC) and sodium carboxymethyl cellulose (CMC-Na). Structural studies and theoretical calculations results suggest that CNC can stabilize the interface between the MXD-DES and water, leading to the formation of Pickering emulsions. The rheological properties and stabilities of MXD Pickering emulsions were enhanced through gelation using CMC-Na, which highlights the good compatibility and effectiveness of natural polysaccharides in emulsion gels. Due to the particle size of emulsion droplets (679 nm) and the rheological properties of emulsion gel, the fabricated MXD formulations show in vivo hair regrowth promotion and hair follicle targeting capabilities. Interestingly, the MXD Pickering emulsion-based formulations exert therapeutic effects by upregulating the expression of hair growth factors. The proposed nanodrug strategy based on supramolecular strategies of CNC and CMC-Na provides an interesting avenue for androgenetic alopecia treatment.

Incorporating surfactants into PCL microneedles for sustained release of a hydrophilic model drug

Polymeric microneedles (MNs) are widely used for sustained drug release due to their distinct advantages over other types of MNs. Poly-ε-caprolactone (PCL) stands out as a biodegradable and biocompatible hydrophobic polymer commonly employed in drug delivery applications. This study explores the impact of surfactants on the encapsulation and release rate of a model hydrophilic drug, minoxidil (MXD), from PCL MNs. Three nonionic surfactants, Tween 80, Span 60, and polyethylene glycol (PEG), were integrated into PCL MNs at varying concentrations. Compared to the other types of surfactants, PEG-containing PCL MNs exhibit enhanced insertion capabilities into a skin-simulant parafilm model and increased mechanical strength, suggesting facile penetration into the stratum corneum. Furthermore, MXD-PEG MNs show the highest encapsulation efficiency and are further characterized using FTIR, DSC and XRD. Their mechanical strength against different static forces was measured. The MNs exhibit a sustained release pattern over 20 days. Eventually, MXD-PEG MNs were subjected to penetration testing using chicken skin and required minimal insertion forces with no observed MN failure during experimentation even after compression with the maximum force applied (32 N per patch). Taken together, the present work demonstrates the feasibility of incorporating nonionic surfactants like PEG into the tips of hydrophobic PCL MNs for sustained delivery of a model hydrophilic drug. This formulation strategy can be used to improve patient compliance by allowing self-administration and achieving prolonged drug release.

Improvement of the Thermal Stability and Aqueous Solubility of Three Matrine Salts Assembled by the Similar Structure Salt Formers

Matrine (MAT), a natural Chinese herbal medicine, has a unique advantage in the treatment of various chronic diseases. However, its low melting point, low bioavailability, and high dosage restrict its subsequent development into new drugs. In this study, three kinds of MAT salts, namely, MAT-2,5-dihydroxybenzoic acid (MAT-25DHB), MAT-2,6-dihydroxybenzoic acid (MAT-26DHB), and MAT-salicylic acid-hydrate (MAT-SAL-H2O), were designed and synthesized to improve the drugability of MAT. The three salts were characterized by using various analytical techniques, including single-crystal X-ray diffractometry, powder X-ray diffractometry, differential scanning calorimetry, thermogravimetry, and infrared spectroscopy. The results of the thermal stability evaluation showed that the formation of salts improved the stability of MAT; MAT-25DHB is the most stable salt reported at present. The results of aqueous solubility showed that the solubility of MAT-25DHB was higher than that of MAT, while that of MAT-26DHB and MAT-SAL-H2O were less. Given that the MAT-25DHB salt further improved the solubility of MAT, it is expected to be subjected to further research as an optimized salt. Lattice energy and solvation free energy are important factors affecting the solubility of salts; the reasons for the changes of solubility and stability of three kinds of salts are explained by calculating them.