High-Intensity Focused Ultrasound-Induced Disulfide Mechanophore Activation in Polymeric Nanostructures for Molecule Release

Ultrasound(US)activation of mechanophores in polymers that initiates cascade chemical reactions is a promising strategy for on-demand molecule release.However,the typical US frequency used for mechanochemistry is around 20 kHz,producing inertial cavitation that exceeds the tolerance threshold of biological systems.Here,high-intensity focused US(HIFU)as a mechanical stimulus is introduced to drive the activation of disulfide mechanophores in hyperbranched star polymers(HBSPs)and microgels(MGLs).The mechanism of molecular release is attributed to the thiol-disulfide exchange reaction and subsequent intramolecular cyclization.We reveal that HBSPs and MGLs effectively transduce HIFU as mechanical input to chemical output,demonstrated by the quantification of the release of fluorescent umbelliferone(UMB).Moreover,an in vitro study of drug release is carried out using camptothecin as the model drug,which is covalently loaded in MGLs,demonstrating the potential of our system for controlled drug delivery to cancer cells.

Ultrasound responsive microcapsules for antibacterial nanodrug delivery

The development of ultrasound-responsive microcapsule structures has resulted in several spatiotemporally controlled drug delivery systems for macromolecular cargoes,including proteins,nucleic acids,and even cells for biomedical applications.However,utilizing microcapsules to transport small molecular cargoes remains a challenge,because the leakage of drugs before ultrasound irradiation might cause side effects such as the undesired toxicity and the decrease of effective drug concentration at the target site.Herein,we present a novel strategy to tackle these shortcomings by employing nanodrugs which refers to nanoparticles coated with small molecule drugs.We showed that the drug leakage was prevented when encapsulating the nanodrug in microcapsules.Moreover,the fabricated drug delivery system was responsive not only to unfocused high-intensity ultrasound but also to the clinically relevant high-intensity focused ultrasound.Finally,as a proof of concept,we showed that the antibacterial activity of the nanodrug@Microcapsules could be activated by applying ultrasound in situ.These results may provide new insights into the development of ultrasound triggered small molecule drug delivery assisted by metallic nanoparticles.

Global attractivity of the predator-prey system for cotton aphid and seven-spot ladybird beetle with stage structure

It is well known that the cotton aphid is the major pest in cotton fields of Northwest China, and seven-spot ladybird is an important natural enemy among the various possi- ble natural enemies of cotton aphid. In order to increase the applications of population dynamics in integrated pest management and control the cotton aphids biologically, we need to understand the population dynamics of cotton aphid and their natural enemies. A delay predator prey system on cotton aphid and seven-spot ladybird beetle are pro- posed in this paper. Based on the comparison theorem and an iterative method, we investigate the global attra^tivity of the equilibrium points which have important bio- logical meanings. Furthermore, some numerical simulations were carried out to illustrateand expand our theoretical results, in which a conjecture to generalize the well-known Theorem 16.4 in H. R. Thiemes book was put forward, which was taken as the open problem. The numerical simulations show coexistence of periodic solution, confirming the theoretical prediction.