Abstract Polypeptide materials offer scalability, biocompatibility, and biodegradability, rendering them an ideal platform for biomedical applications. However, the preparation of polypeptides with specific functional groups, such as semicarbazide moieties, remains challenging. This work reports, for the first time, the straightforward synthesis of well‐defined methoxy‐terminated poly(ethylene glycol)‐ b ‐polypeptide hybrid block copolymers (HBCPs) containing semicarbazide moieties. This synthesis involves implementing the direct polymerization of environment‐stable N ‐phenoxycarbonyl‐functionalized α‐amino acid (NPCA) precursors, thereby avoiding the handling of labile N ‐carboxyanhydride (NCA) monomers. The resulting HBCPs containing semicarbazide moieties enable facile functionalization with aldehyde/ketone derivatives, forming pH‐cleavable semicarbazone linkages for tailored drug release. Particularly, the intracellular pH‐triggered hydrolysis of semicarbazone moieties restores the initial semicarbazide residues, facilitating endo‐lysosomal escape and thus improving therapeutic outcomes. Furthermore, the integration of the hypoxic probe ( Ir(btpna)(bpy) 2 ) into the pH‐responsive nanomedicines allows sequential responses to acidic and hypoxic tumor microenvironments, enabling precise detection of metastatic tumors. The innovative approach for designing bespoke functional polypeptides holds promise for advanced drug delivery and precision therapeutics.
Ethnopharmacological relevance: In traditional Chinese herbal medicine, rhubarb is said to remove accumulation with purgation, clearing heat, and discharging fire. Modern pharmacology has shown that rhubarb extract has a purgative effect when given to experimental animals in an appropriate dose. However, the active components and their mechanism of action are still not clearly defined.Aim of the study: The current research aimed to evaluate the synergistic stool-softening effects and explore the action mechanism of rhubarb free anthraquinones (RhA) and their monomers on constipation in rats.Materials and methods: A rat model of water deficit-induced constipation was established to induce constipation, and these rats were treated with RhA and its monomers. ELISA, histopathology, immunohistochemistry, qPCR and Western blotting were conducted to explore the possible mechanism of action of RhA and its monomers.Results: RhA, aloe-emodin, rhein, and chrysophanol showed stool-softening activity, and the combination of aloe-emodin and rhein had the strongest softening effect on faecal pellets. Aloe-emodin, rhein, and chrysophanol significantly increased the serum levels of vasoactive intestinal peptide (VIP), motilin (MTL), and substance P (SP), upregulated the expression of VIP, cyclase-associated protein 1 (CAP1), protein kinase A (PKA), cystic fibrosis transmembrane conductance regulator (CFTR), aquaporin 3 (AQP3), aquaporin 4 (AQP4), and aquaporin 8 (AQP8), decreased the expression of epithelial sodium channel (ENaC) and Na+/H+ exchanger 3 (NHE3), and reduced the colonic tissue concentration of Na+-K+-ATPase in the constipated rats. Osmolality of colonic fluid in model rats treated by RhA, aloe-emodin, rhein, and chrysophanol was increased.Conclusion: Aloe-emodin, rhein, and chrysophanol were the stool-softening components of the RhA extract. RhA upregulated VIP expression, activated the cyclic adenosine monophosphate protein kinase A (cAMP/PKA) pathway, and further stimulated CFTR expression while inhibiting NHE3 and ENaC expression, resulting in a hypertonic state in the colonic lumen. Water transport could then be driven by an osmotic gradient, which in turn led to the upregulation of AQP3, AQP4, and AQP8 expression. In addition, RhA likely improved gastrointestinal motility by increasing serum VIP, SP, and MTL concentrations, thus promoting faecal excretion.
Gas-filled microbubbles (MBs) have been clinically used as ultrasound (US) contrast agents for disease diagnosis and treatment. However, it remains a great challenge to resolve the dilemma of stability and contrast enhancement of MBs. Herein, amphiphilic copolypeptides bearing fluorinated blocks are synthesized to stabilize perfluorocarbon (PFC)-filled MBs, exhibiting unique stability under both long-term storage and US imaging conditions. The fluorinated inner layer reduces the internal Laplace pressure and greatly improves the stability of MBs, which can be further reinforced by crosslinking of the dipropargyl-containing middle blocks. To overcome the suppressed nonlinear oscillation of polymer shells, maleimide groups are introduced onto the surface of MBs, enabling in situ reaction with plasma proteins to enhance second harmonic signals without compromising the stability of MBs, conferring better US imaging performance than that of SonoVueTM MBs.
Abstract Gas‐filled microbubbles (MBs) have been clinically used as ultrasound (US) contrast agents for disease diagnosis and treatment. However, it remains a great challenge to resolve the dilemma of stability and contrast enhancement of MBs. Herein, amphiphilic copolypeptides bearing fluorinated blocks are synthesized to stabilize perfluorocarbon (PFC)‐filled MBs, exhibiting unique stability under both long‐term storage and US imaging conditions. The fluorinated inner layer reduces the internal Laplace pressure and greatly improves the stability of MBs, which can be further reinforced by crosslinking of the dipropargyl‐containing middle blocks. To overcome the suppressed nonlinear oscillation of polymer shells, maleimide groups are introduced onto the surface of MBs, enabling in situ reaction with plasma proteins to enhance second harmonic signals without compromising the stability of MBs, conferring better US imaging performance than that of SonoVue TM MBs.
Controlled polypeptide synthesis via α -amino acid N -carboxylic anhydride (NCA) polymerization using conventional primary amine initiators encounters two major obstacles: (i) normal amine mechanism (NAM) and activated monomer mechanism (AMM) coexist due to amine basicity and nucleophilicity and (ii) NCA is notoriously sensitive towards moisture and heat and unstable upon storage. We serendipitously discover that N -phenoxycarbonyl-functionalized α -amino acid (NPCA), a latent NCA precursor, could be polymerized solely based on NAM with high initiating efficiency by using primary amine hydrochloride as an initiator. The polymerization affords well-defined polypeptides with narrow polydispersity and high-fidelity terminal functionalities, as revealed by the clean set of MALDI-TOF MS patterns. We further demonstrate successful syntheses of random and block copolypeptides, even under open-vessel conditions. Overall, the integration of moisture-insensitive and air-tolerant NPCA precursors with stable primary amine hydrochloride initiators represents a general strategy for controlled synthesis of high-fidelity polypeptides with sophisticated functions.
Two new C21 steroidal glycosides were isolated from Cynanchum wallichii Wight. Their structures were elucidated as caudatin-3-O-β-d-glucopyranosyl-(1 → 4)-β-d-oleandropyranosyl-(1 → 4)-β-d-cymaropyranosyl-(1 → 4)-β-d-digitoxopyranoside (1) and caudatin-3-O-β-d-glucopyranosyl-(1 → 4)-β-d-cymaropyranosyl-(1 → 4)-β-d-oleandropyranosyl-(1 → 4)-β-d-cymaropyranosyl-(1 → 4)-β-d-digitoxopyranoside (2) by spectroscopic methods including 1D and 2D NMR experiments.
The inherent structural instability and very low bioavailability of ligustilide (Lig) lead to the limited application of the clinical neuroprotection. We developed a stabilised method for Lig, which involved a chemical synthesis between cyclopropylamine and the active phthalides extract included Lig from
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