Fabrication of Black Silicon Microneedle Arrays for High Drug Loading.

Silicon microneedle (Si-MN) systems are a promising strategy for transdermal drug delivery due to their minimal invasiveness and ease of processing and application. Traditional Si-MN arrays are usually fabricated by using micro-electro-mechanical system (MEMS) processes, which are expensive and not suitable for large-scale manufacturing and applications. In addition, Si-MNs have a smooth surface, making it difficult for them to achieve high-dose drug delivery. Herein, we demonstrate a solid strategy to prepare a novel black silicon microneedle (BSi-MN) patch with ultra-hydrophilic surfaces for high drug loading. The proposed strategy consists of a simple fabrication of plain Si-MNs and a subsequent fabrication of black silicon nanowires. First, plain Si-MNs were prepared via a simple method consisting of laser patterning and alkaline etching. The nanowire structures were then prepared on the surfaces of the plain Si-MNs to form the BSi-MNs through Ag-catalyzed chemical etching. The effects of preparation parameters, including Ag+ and HF concentrations during Ag nanoparticle deposition and [HF/(HF + H2O2)] ratio during Ag-catalyzed chemical etching, on the morphology and properties of the BSi-MNs were investigated in detail. The results show that the final prepared BSi-MN patches exhibit an excellent drug loading capability, more than twice that of plain Si-MN patches with the same area, while maintaining comparable mechanical properties for practical skin piercing applications. Moreover, the BSi-MNs exhibit a certain antimicrobial activity that is expected to prevent bacterial growth and disinfect the affected area when applied to the skin.

Micro-structured P-N junction surfaces: large-scale preparation, antifouling properties, and a synergistic antibacterial mechanism.

Constructing an antifouling surface cost-effectively is vitally important for many applications. Herein, a series of silicon substrates with micro-pyramid structures and p-n junctions were fabricated following a simple industrial processing flow, among which the p+n-Si substrate, fabricated through boron doping of a micro-pyramid structured n-type silicon wafer, exhibited the most pronounced antibacterial performance. Broad-spectrum bactericidal and bacteriostatic activity of p+n-Si under ambient light illumination was observed, with an inhibition ability of 73-100% compared to that of a bare glass against both airborne and contact-transmitted bacteria in the intensive care unit. The synergetic effect of mechanical rupture and electric injury was supposed to be responsible for the potent antibacterial activity. This work proposes a state-of-the-art concept that p-n junctions enhance the anti-infection ability of micro-structured surfaces and provide a promising strategy for fabricating practical antifouling surfaces with a large-size, a facile manufacturing procedure, and gentle working conditions, as well as broad-spectrum and physical antibacterial mechanisms.

Dramatically Promoted Swelling of a Hydrogel by Pillar[6]arene-Ferrocene Complexation with Multistimuli Responsiveness.

The swelling-shrinking transition of hydrogels is crucial for their wide applications such as actuators and drug delivery. We hereby fabricated a smart hydrogel with ferrocene groups on pendant of polymer networks. While it was immersed in the water-soluble pillar[6]arene (WP6) aqueous solution, the hydrogel was dramatically swollen, which was an approximately 11-fold promotion in weight compared with that in pure water, due to the formation of the inclusion complexes between WP6 and ferrocene groups in the hydrogel. In particular, the well-swollen hydrogel exhibited good responsiveness to multistimuli including temperature, pH, redox, and competitive guests by tuning the dissociation/formation of WP6-ferrocene inclusion complexes or the strength of their charges. Meanwhile, potential application of such a smart hydrogel in pH-responsive drug release was demonstrated as well.

Dynamic self-inclusion behavior of pillar[5]arene-based pseudo[1]rotaxanes.

It was found that spontaneous isomerization takes place between three isomers of a pillar[5]arene (P5)-based pseudo[1]rotaxane. The isomerization process could be monitored by (1)H NMR spectra in polar solvent and the geometric configurations of the three isomers were further evaluated by theoretical calculations. In the threaded forms, the alkyl side chain might be preorganized by intramolecular N-HO bonds between the urea group of the side chain and the methoxy group of the P5 and further stabilized by multiple interactions, including H-bonding, C-H∙∙∙π interactions, and the steric effect of the N-Boc moiety. These cooperative interactions greatly enhance the stability of the threaded form in polar solvent, and endow it with very special self-inclusion behavior.

The self-complexation of mono-urea-functionalized pillar[5]arenes with abnormal urea behaviors.

Mono-urea-functionalized pillar[5]arenes were prepared which exhibited abnormal urea behaviors. They were shown to form pseudo[1]rotaxanes with poor anion binding abilities in solution and [c2]daisy chains with an abnormal urea motif in the solid state.

Novel [2]pseudorotaxanes constructed by self-assembly of bis-urea-functionalized pillar[5]arene and linear alkyl dicarboxylates.

A bis-urea-functionalized pillar[5]arene has been synthesized and shown to form [2]pseudorotaxanes spontaneously with linear alkyl dicarboxylates in highly polar solvent DMSO, in which the hydrogen bonding interactions between the bis-urea hydrogens and dicarboxylate oxygens play an important role in stabilizing the novel [2]pseudorotaxanes alongside C-Hπ interactions.

Pillar[5]arene-based polymeric architectures constructed by orthogonal supramolecular interactions.

Ureidopyrimidinone functionalized pillar[5]arene (UPyP5) was synthesized and employed to complex with a bisparaquat derivative (G) to form supramolecular polymers at relatively high concentration. The orthogonal binding interactions including quadruple hydrogen bonding and host-guest interaction should play vital roles in the construction of this linear assembly.