Oil soluble surfactants as efficient foam stabilizers

Polymeric nanoparticles containing babassu oil: a proposed drug delivery system for controlled release of hydrophilic compounds

Different drug delivery systems are prepared on the nanoscale to improve performance in drug formulations, such as nanoparticles or nanoemulsions. Polymeric nanoparticles have been used to encapsulate drugs for several applications because of some characteristics of these carriers to control drug delivery, transport molecules to a specific tissue, protect the drugs, and increase drug bioavailability. When using nanocapsules, an essential parameter for encapsulating different hydrophilic or lipophilic molecules is the characteristics of the core. Babassu oil (BBS) is a natural product from Brazil, composed majoritary of short-chain saturated fatty acids. BBS has an elevated hydrophilic-lipophilic balance (HLB), which may promote interaction of the oil with hydrophilic drugs. In this study, we developed and characterized particles containing babassu oil, solely or combined with sorbitan monostearate (Span® 60) or medium chain triglycerides (MCT) in the core to test different HLB and evaluated the encapsulation of a model hydrophilic molecule. Different techniques were used to characterize all formulations in terms of size and distribution, and in vitro drug release by dialysis technique was performed. The BBS was also characterized and presented 46,05 ± 1,11% and 15,38 ± 0,06 of lauric and myristic acid, respectively; saponification index of 248.87 ± 0.64mg of KOH per gram of BBS, and no oxidation of the oil was indicated by means of peroxide index. Evaporation of solvent carried in the room or reduced pressure influenced the particles' size; nevertheless, all had a z-average smaller than 220nm. Nanoparticles with a ratio of among aqueous phase and organic phase of 2.8 were considered adequate to encapsulate diclofenac sodium. The particle size/zeta potential was 189.83 ± 7.86nm / -10.39 ± 2.52mV, 156.80 ± 4.77nm / -9.27 ± 4.61mV, and 168.87 ± 5.22nm / -12.98 ± 4.66mV to nanoparticles prepared with BBS + MCT, BBS, and BBS + Span® 60, respectively. All formulations exhibited an amount of drug content close to the theoretical amount (1.0mgmL^-1), and no difference was observed in the release profile among the three cores. Formulation containing only babassu oil in the core displayed 66.78 ± 15.62% of encapsulation efficiency to diclofenac sodium, the highest value among all formulations tested. Results demonstrate that the innovative nanoparticles containing BBS promote the encapsulation of a model hydrophilic molecule, and other components can be evaluated to change the core's hydrophilicity and encapsulation of molecules.

Interplay between bulk aggregates, surface properties and foam stability of nonionic surfactants

In our previous study (Mustan et al. 2021) we showed that foams formed from two oil-soluble nonionic surfactants (Span 60 and Brij 72) can remain stable for more than 10 days at room temperature at high sugar concentration. The major aim of the current study is to reveal the interrelation between the surfactant structure and foam stability by investigating 6 polyoxyethelene alkyl ethers and 12 fatty acid esters with a wide variety of hydrophobic chain lengths (C12; C16; C18 and C18:1) and hydrophilic head-groups (sorbitol, glycerol, sucrose). Foams stable for more than 100 days at room temperature are obtained when sucrose palmitate or stearate (P1670 or S1670) are used as surfactants. This exceptional foam stability is related to the gelation of the aqueous phase and to the formation of solid adsorption layer with zero surface tension upon compression, thus preventing water drainage and decelerating the bubble Ostwald ripening. The foam stability decreases with (i) increasing the number of EO groups in polyoxyethylene alkyl ethers and in fatty acid sorbitan esters; (ii) decreasing the number of C-atoms in the surfactant tail for all studied surfactants; (iii) addition of double bond in the surfactant tail. The lower foam stability in all three cases is related to the worse packing of the surfactant molecules within the adsorption layer, leading to faster Ostwald ripening and subsequent bubble coalescence. The diesters present as admixture in the fatty acid esters play an important role in the foam stabilization by further compacting the adsorption layers and lowering the rate of Ostwald ripening. These conclusions can be used as a predictive tool for surfactant selection in the development of food or pharmaceutical foam concentrates that can be diluted before final use.