Dual character of surface engineering on SN38 prodrug nano-assemblies: divergent effects on in vitro and in vivo...

Surface engineering has emerged as a promising strategy to enhance the performance of nanomedicines. In particular, the PEGylation levels for chemotherapy drug 7-Ethyl-10-hydroxycamptothecin (SN38) prodrug nanoparticles (NPs) play a crucial role in determining their stability, drug release kinetics, cytotoxicity, cellular uptake, in vivo pharmacokinetics, biodistribution, and antitumor efficacy. The study aims to investigate the surface engineering for chemotherapy drugs, providing new solutions for improving their in vivo delivery.

We systematically evaluated the effects of different PEGylation levels on NPs (W_DSPE-mPEG2k/W_prodrug; 0%, 5%, 20%, 40%, 60%, 80%, 100%, 150%, and 200% NPs) incorporated on SN38 prodrug NPs via surface engineering. Drug release was measured using high-performance liquid chromatography (HPLC), while cytotoxicity was assessed via the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Cellular uptake was accurately quantified using liquid chromatography-mass spectrometry (LC-MS). The in vivo pharmacokinetics of the NPs were evaluated in Sprague-Dawley rats, and the biodistribution and antitumor efficacy were assessed using a CT26 colon tumor-bearing BALB/c mice model. Additionally, we examined intestinal toxicity to evaluate the safety profile.

All the different PEGylation levels of SN38 prodrug NPs exhibited high drug loading (> 25%) but distinct behaviors depending on the PEGylation level. Low PEGylation (20%) led to poor colloidal stability, reduced cellular uptake, and rapid clearance by the mononuclear phagocyte system (MPS), resulting in unfavorable pharmacokinetics. Moderate PEGylation (80%) improved in vitro stability and uptake but remained insufficient to prevent rapid clearance in vivo. In contrast, high PEGylation (150%) significantly enhanced pharmacokinetic profiles, prolonged circulation, and increased tumor accumulation. The 150% NPs also showed superior antitumor efficacy without triggering anti-polyethylene glycol (PEG) immune responses or accelerated blood clearance (ABC) effects. Although high PEGylation slightly reduced cellular uptake, it conferred essential stability for systemic delivery, improving in vivo therapeutic outcomes.

The high PEGylation (150% NPs) exhibited the best antitumor effect and the lowest degree of intestinal toxicity. Our findings underscore the critical impact of PEGylation level on enhancing the performance and safety of SN38 prodrug NPs.