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pH-sensitive betulinic acid (BA) polymer prodrug nanoparticles, have been proposed. The carboxyl group-terminated poly[2-(3-butenyl)-2-oxazoline] (PBuOx-COOH) is prepared by cationic ring-opening polymerization (CROP) of the 2-(3-butenyl)-2-oxazoline (BuOx) using ethyl 3-bromopropionate as initiator followed by hydrolysis with methanolic KOH. Folic acid (FA) was connected with the PBuOx-COOH through polyethylene glycol (PEG) as spacer forming the FA-PEG-PBuOx. Thiol-modified betulinic acid (BA-SH) is conjugated to the side chains of FA-PEG-PBuOx by thio-ene reaction endowed the FA-PEG-PBuOx/BA with the acid-liable β-thiopropionate linkages. Additionally, the cellular uptake of the prodrug nanoparticles also showed vital potential for folate-receptor-positive HeLa cells. [ABSTRACT FROM AUTHOR]

Poly(2-oxazoline)-based nanoparticles with AIE feature were prepared for targeted cell imaging. First, P(EtOx-BuOx) was fabricated by subsequent cationic ring-opening polymerization (CROP). Then, the folate was attached to the end chains of P(EtOx-BuOx). AIE-active TPEMN was conjugated to the side chains of P(EtOx-BuOx) through "thio-ene" click reactions. Cellular experiments demonstrated that the nanocomposites had well dispersity in the physiological environment and could be internalized by folate receptor (FR)-positive cells. We envision that this research endows a simple approach to the fabrication of stable fluorescent polymeric nanocomposites, which display favorable biocompatibility and immense potential for applications in biological imaging and cell detection. [ABSTRACT FROM AUTHOR]