Sequential drug release via chemical diffusion and physical barriers enabled by hollow multishelled structures

Abstract

Hollow multishelled structures (HoMSs), with relatively isolated cavities and hierarchal pores in the shells, are structurally similar to cells. Functionally inspired by the different transmission forms in living cells, we studied the mass transport process in HoMSs in detail. In the present work, after introducing the antibacterial agent methylisothiazolinone (MIT) as model molecules into HoMSs, we discover three sequential release stages, i.e., burst release, sustained release and stimulus-responsive release, in one system. The triple-shelled structure can provide a long sterility period in a bacteria-rich environment that is nearly 8 times longer than that of the pure antimicrobial agent under the same conditions. More importantly, the HoMS system provides a smart responsive release mechanism that can be triggered by environmental changes. All these advantages could be attributed to chemical diffusion- and physical barrier-driven temporally-spatially ordered drug release, providing a route for the design of intelligent nanomaterials.

Delicate Control on the Shell Structure of Hollow Spheres Enables Tunable Mass Transport in Water Splitting

“…Especially, the CoP HoMSs with close duplicated shells are better to be wetted than CoP HoMSs with porous bubble‐like shells and that with non‐duplicated solid shells (Figure 3 b–d). The greater hydrophilicity can be understood from the equation of the liquid height induced by capillary force, h =2 σ cos θ /( ρgr ), which means the height ( h ) is inversely proportional to the capillary radius ( r ) [8] . Therefore, the small space between shells of D‐CoP‐HoMSs can provide a stronger capillary force to drive liquid diffusion.…”

“…The greater hydrophilicity can be understood from the equation of the liquid height induced by capillary force, h = 2s cosq/ (1gr), which means the height (h) is inversely proportional to the capillary radius (r). [8] Therefore, the small space between shells of D-CoP-HoMSs can provide a stronger capillary force to drive liquid diffusion. Particularly after the release of produced gas, the liquid can rapidly replenish the space where the bubble disappears to ensure the fast reaction kinetics.…”

“…This structure evolution is experimentally realized for the first time, and then these materials were conducted for a typical multi-phase reaction of water splitting. [6] Benefitting from the structure advantages, the CoP HoMSs with close duplicated shells facilitate the escape of gas bubbles because of unbalanced Laplace pressure, [7] and enhance the driving force for liquid diffusion [8] due to capillary action, thus achieving excellent catalytic performance in both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER).…”

Hollow structures as drug carriers: Recognition, response, and release

“…Notably, spatiotemporal ordering was found to be a unique property of HoMS in drug release. Since HoMS can provide different storage sites and various interactions for drug molecules, [76], the drugs adsorbed on the surface are easily released at the initial stage, resulting in burst release; the drugs in the cavity through π-π stacking interactions contribute to the following sustained release stage and also the responsive release stage; the drug molecules that form hydrogen bonds with the surface also contribute to part of the responsive release. Therefore, it is a multi-level release process induced by physical barriers and chemical interaction.…”

“…Zhao et al [76] used hollow multi-shelled TiO2 as a drug carrier and antibacterial agent methylisothiazolinone (MIT) as a model drug. MIT molecules adsorbed in the outer surface can be discharged quickly as the weaker driving force required, thus bringing out the bactericidal concentration.…”