Due to the multiple hydroxyl groups in its structure, hydroxytyrosol (HT) is very sensitive to air and light and has very strong instability and hydrophilicity that affect its biological activity. This study attempted to prepare liposomes containing water-soluble HT to improve the bioavailability and biocompatibility of the target drug. The preparation process factors (temperature, mass ratio of phospholipid (PL) and cholesterol (CH), Tween-80 volume, HT mass) were studied and response surface methodology (RSM) was applied to optimize the conditions. The results demonstrated that by using a temperature of 63 °C, mass ratio of PL and CH 4.5:1, HT mass 5 mg and Tween-80 volume of 6 mL, HT liposomes with an encapsulation efficiency (EE) of 45.08% were prepared. It was found that the particle sizes of the HT liposomes were well distributed in the range of 100–400 nm. Compared to free HT, prepared HT liposomes had better stability and a distinct slow release effect in vitro. Besides, HT liposomes presented better DPPH radical scavenging activity than free HT, which could be due to the fact that HT was encapsulated fully inside the liposomes. In addition, the encapsulation mechanism of HT was evaluated. In summary, the results indicated that HT liposome could enhance the antioxidant activity and was a promising formulation for prolonging the biological activity time of the target drug.

Reactive species (RS) play a critical role in postoperative complications in the medical application of lasers. From the mechanistic point, the RS arising from laser irradiation are produced from two channels: ionization and dissociation of water in the breakdown plasma, and the violent collapse of the laser-induced cavitation bubble. The latter channel is especially important for nanosecond pulses but poorly understood. In this paper, we conducted a simulation of the chemical reactions coupled with bubble dynamic calculation to quantitatively identify the RS produced in the collapsing bubble. The generation mechanism is explored by the analysis of the reaction pathway. Our calculation shows that while the absolute quantity of the produced RS is small, very high concentrations can be achieved inside the strongly compressed bubble. The initial composition of the bubble recovered from plasma recombination and expansion is found to influence the chemical reactions significantly. Unlike the direct splitting of water molecules in radiolysis and photolysis, the RS productions mainly involve the decomposition of hydrogen peroxide and the reactions between hydrogen, oxygen, and various free radicals. Furthermore, the produced RS is observed to increase with pulse energy as a result of the larger-sized bubbles and more violent collapses. These findings complement our current knowledge of RS in laser surgery and can be used to develop strategies to mitigate the adverse effects or exploit the associated benefits.