The use of microneedles (MNs), an innovative transdermal
technology,
enables efficient, convenient, painless, and controlled-release drug
delivery. Porous microneedles (pMNs), special MNs with abundant interconnected
pores that can produce capillary action, are gaining increasing attention
as a novel MNs technology. pMNs can actively adsorb bioactive ingredients
from solutions of drugs or vaccines for in vivo delivery or from interstitial
skin fluids (ISFs) for wearable and point-of-care testing (POCT) products.
Different pore sizes and porosities of pMNs can be achieved with different
materials and preparation processes, which makes the application of
pMNs adaptable to multiple scenarios. In addition, easier and faster
detection will be accomplished by the smart combination of pMNs with
other detection technologies. This paper aims to summarize the recent
research progress of pMNs, focusing on the influence of various materials
and their corresponding preparation methods on its structure and function
display, discussing the key issues and looking forward to the future
development.
The emergence of microneedle arrays (MNAs) as a novel, simple, and minimally invasive administration approach largely addresses the challenges of traditional drug delivery. In particular, the dissolvable MNAs act as a promising, multifarious, and well-controlled platform for micro-nanotransport in medical research and cosmetic formulation applications. The effective delivery mostly depends on the behavior of the MNAs penetrated into the body, and accurate assessment is urgently needed. Advanced imaging technologies offer high sensitivity and resolution visualization of cross-scale, multidimensional, and multiparameter information, which can be used as an important aid for the evaluation and development of new MNAs. The combination of MNA technology and imaging can generate considerable new knowledge in a cost-effective manner with regards to the pharmacokinetics and bioavailability of active substances for the treatment of various diseases. In addition, noninvasive imaging techniques allow rapid, receptive assessment of transdermal penetration and drug deposition in various tissues, which could greatly facilitate the translation of experimental MNAs into clinical application. Relying on the recent promising development of bioimaging, this review is aimed at summarizing the current status, challenges, and future perspective on in vivo assessment of MNA drug delivery by various imaging technologies.
Brucine chloromethochloride and strychnine chloromethochloride, the two chloromethochloride derivatives formed during the extraction of Semen Strychni in which dichloromethane was used as the extracting solvent, were isolated and purified by high-speed countercurrent chromatography for the first time. The two-phase solvent system composed of chloroform/methanol/0.3 mol/L hydrochloric acid (4:3:2, v/v/v) was selected for separation. From 300 mg of the crude extracts, 56.2 mg of brucine chloromethochloride and 60.2 mg of strychnine chloromethochloride were obtained with the purity of 99.78 and 96.99%, respectively, and the structures were confirmed by mass spectrometry, H, C, and two-dimensional NMR spectroscopy. The results indicated that the present method is a powerful technology for large-scale isolation of alkaloids from Semen Strychni.
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