A recent overview of surfactant-drug interactions and their importance

Carboxymethyl cellulose-based rotigotine nanocrystals-loaded hydrogel for increased transdermal delivery with alleviated skin irritation

Transdermal rotigotine (RTG) therapy is prescribed to manage Parkinson's disease (Neupro® patch). However, its use is suffered from application site reactions. Herein, drug nanocrystalline suspension (NS)-loaded hydrogel (NS-HG) employing polysaccharides simultaneously as suspending agent and hydrogel matrix was constructed for transdermal delivery, with alleviated skin irritation. RTG-loaded NS-HG was prepared using a bead-milling technique, employing sodium carboxylmethyl cellulose (Na.CMC) as nano-suspending agent (molecular weight 90,000 g/mol) and hydrogel matrix (700,000 g/mol), respectively. NS-HG was embodied as follows: drug loading: ≤100 mg/mL; shape: rectangular crystalline; crystal size: <286.7 nm; zeta potential: -61 mV; viscosity: <2.16 Pa·s; and dissolution rate: >90 % within 15 min. Nuclear magnetic resonance analysis revealed that the anionic polymers bind to RTG nanocrystals via charge interaction, affording uniform dispersion in the matrix. Rodent transdermal absorption of RTG from NS-HG was comparable to that from microemulsions, and proportional to drug loading. Moreover, NS-HG was skin-friendly; erythema and epidermal swelling were absent after repeated application. Further, NS-HG was chemically stable; >95 % of the drug was preserved up to 4 weeks under long term (25 °C/RH60%), accelerated (40 °C/RH75%), and stress (50 °C) storage conditions. Therefore, this novel cellulose derivative-based nanoformulation presents a promising approach for effective transdermal RTG delivery with improved tolerability.

The interaction between formylphenoxyacetic acid derivatives (chalcone and flavones) and ionic surfactants: Insights into binding constants, solubilisation and physiochemical properties

In this study, UV-vis spectroscopy was employed to investigate the interaction between formylphenoxyacetic acid (FPAA) and its derivatives (chalcone and flavones) with ionic surfactants (SDS, CTAB, and DTAB) in different physiological environments. Changes in the physiochemical properties of FPAA chalcone and flavones including binding constants, partitioning constants, and Gibbs free energy were observed which were influenced by the presence of ionic surfactants computed using mathematical models. The solubilization of the targeted compounds in the ionic surfactants was determined through the binding constant (Kb). The results of the present study indicated that electrostatic interactions played a significant role in the solubilization of the targeted compounds in SDS, CTAB, and DTAB. At pH 4.1, FPAA chalcone exhibited stronger binding affinity with SDS compared to CTAB and DTAB. However, at pH 7.4, chalcone showed stronger binding with DTAB compared to SDS, while negligible interaction with CTAB was observed at pH 7.4. The flavones demonstrated stronger binding with DTAB at pH 7.4 compared to SDS and CTAB and it exhibited strong bonding with CTAB at pH 4.1. The negative values of the Gibbs free energy for binding (ΔGb˚) and partitioning (ΔGp˚) constants displayed the spontaneity of the process. However, FPAA chalcone with SDS and FPAA flavones with DTAB furnished positive ΔGb˚, indicating a non-spontaneous process.

Effects of surfactants on the adsorption of norfloxacin onto ferrihydrite: comparison between anionic and cationic surfactants

There is little information on how widespread surfactants affect the adsorption of norfloxacin (NOR) onto iron oxide minerals. In order to elucidate the effects of various surfactants on the adsorption characteristics of NOR onto typical iron oxides, we have explored the different influences of sodium dodecylbenzene sulfonate (SDBS), an anionic surfactant, and didodecyldimethylammonium bromide (DDAB), a cationic surfactant, on the interactions between NOR and ferrihydrite under different solution chemistry conditions. Interestingly, SDBS facilitated NOR adsorption, whereas DDAB inhibited NOR adsorption. The adsorption-enhancement effect of SDBS was ascribed to the enhanced electrostatic attraction, the interactions between the adsorbed SDBS on ferrihydrite surfaces and NOR molecules, and the bridging effect of SDBS between NOR and iron oxide. In comparison, the adsorption-inhibition effect of DDAB owning to the adsorption site competitive adsorption between NOR and DDAB for the effective sites as well as the steric hindrance between NOR-DDAB complexes and the adsorbed DDAB on ferrihydrite surfaces. Additionally, the magnitude of the effects of surfactants on NOR adsorption declined with increasing pH values from 5.0 to 9.0, which was related to the amounts of surfactant binding to ferrihydrite surfaces. Moreover, when the background electrolyte was Ca2+, the enhanced effect of SDBS on NOR adsorption was caused by the formation of NOR-Ca2+-SDBS complexes. The inhibitory effect of DDAB was due to the DDAB coating on ferrihydrite, which undermined the cation-bridging effect. Together, the findings from this work emphasize the essential roles of widely existing surfactants in controlling the environmental fate of quinolone antibiotics.

Study on the association and phase separation behavior of surfactants and promethazine hydrochloride: impact of ammonium electrolytes

In the current study, the association and phase separation of cationic tetradecyltrimethylammonium bromide (TTAB) and nonionic Triton X-100 (TX-100) surfactants with promethazine hydrochloride (PMH) were investigated in aqueous ammonium-based solutions. The micellization nature of the TTAB and PMH drug mixture was examined by evaluating critical micelle concentration (CMC) and counterion binding extent (β) at different salt contents and temperatures (298.15-323.15 K). Micelle formation in the TTAB + PMH mixture was enhanced in the presence of ammonium salts, whereas the process was delayed with an increase in temperature in the respective salt solution. With an increase in salt content, the cloud point (CP) of the TX-100 + PMH mixture decreased, which revealed that the respective progression occurred through the salting out phenomenon. In micellization and clouding processes, the changes in free energies ΔG0m and ΔG0c were found to be negative and positive, respectively, demonstrating that the corresponding processes are spontaneous and non-spontaneous. Standard enthalpies (ΔH0m/ΔH0c) and standard entropies (ΔS0m/ΔS0c) for the association and clouding processes, respectively, were also calculated and discussed. The core forces amid TTAB/TX-100 and PMH in the manifestation of electrolytes are dipole-dipole and hydrophobic forces among the employed components according to the values for ΔH0m/ΔH0c and ΔS0m/ΔS0c, respectively.