Astragalus membranaceus (Fisch.) Bge. administered by dissolving microneedles achieves systemic therapeutic effects at low doses

Abstract

ObjectiveTo determine the main components of Astragalus membranaceus (Fisch.) Bge (A. membranaceus, Huang Qi), Astragaloside IV (AIV) and Astragalus polysaccharides (AP), to characterize their properties, evaluate their in vivo efficacy, and to analyze drug diffusion using dissolving microneedle (DMN) technology in vivo. MethodsRespectively, AIV- and AP-loaded DMNs comprising chitosan (CTS) and polyvinyl alcohol (PVA) were prepared via dual-mold forming. Their morphology, mechanical properties, in vivo solubility, and skin irritation characteristics were tested. In vivo efficacy was assessed in cyclophosphamide-induced immunosuppressed mice, in vivo diffusion of AIV and AP by DMNs and conventional methods was compared, and the rheological properties of AIV-CTS-PVA and AP-CTS-PVA mixtures were measured. ResultsSubcutaneous dissolution and absorption of AIV-CTS-PVA and AP-CTS-PVA microneedles (MNs) at low doses (50%–17% of intraperitoneal AIV injection and 12%–4% of intravenous AP injection) reduced the spleen index and acid phosphatase activity in immunosuppressed mouse models, increased the thymus index, and achieved equivalent or better systemic therapeutic effects. Compared with injections, AIV and AP achieved controllable solid-liquid conversion through delivery with CTS-PVA MNs, resulting in highly localized aggregation within 48 h, reducing the initial explosive effect of the drug, and achieving stable and slow drug release. ConclusionThe present study enhances our understanding of the efficacy and remote effects of drug-loaded DMNs from a traditional Chinese medicine (TCM) perspective, thereby promoting the development of precise and efficient delivery of TCM and further expanding the drug-loading range and application scenarios for DMNs.