bm400206m_si_001.pdf (60.05 kB)
In Situ Forming Reduction-Sensitive Degradable Nanogels for Facile Loading and Triggered Intracellular Release of Proteins
journal contribution
posted on 2016-02-19, 12:59 authored by Wei Chen, Meng Zheng, Fenghua Meng, Ru Cheng, Chao Deng, Jan Feijen, Zhiyuan ZhongIn
situ forming reduction-sensitive degradable nanogels were designed
and developed based on poly(ethylene glycol)-b-poly(2-(hydroxyethyl)
methacrylate-co-acryloyl carbonate) (PEG-P(HEMA-co-AC)) block copolymers for efficient loading as well as
triggered intracellular release of proteins. PEG-P(HEMA-co-AC) copolymers were prepared with controlled Mn of 9.1, 9.5, and 9.9 kg/mol and varying numbers of AC units
per molecule of 7, 9 and 11, respectively (denoted as copolymer 1, 2, and 3) by reversible addition–fragmentation
chain transfer copolymerization. These copolymers were freely soluble
in phosphate buffer but formed disulfide-cross-linked nanogels with
defined sizes ranging from 72.5 to 124.1 nm in the presence of cystamine
via ring-opening reaction with cyclic carbonate groups. The sizes
of nanogels decreased with increasing AC units as a result of increased
cross-linking density. Dynamic light scattering studies showed that
these nanogels though stable at physiological conditions were rapidly
dissociated in response to 10 mM dithiothreitol (DTT). Interestingly,
FITC-labeled cytochrome C (FITC–CC) could be readily loaded
into nanogels with remarkable loading efficiencies (up to 98.2%) and
loading contents (up to 48.2 wt.%). The in vitro release
studies showed that release of FITC–CC was minimal under physiological
conditions but significantly enhanced under reductive conditions in
the presence of 10 mM DTT with about 96.8% of FITC–CC released
in 22 h from nanogel 1. In contrast, protein release
from 1,4-butanediamine cross-linked nanogels (reduction-insensitive
control) remained low under otherwise the same conditions. MTT assays
showed that these nanogels were nontoxic to HeLa cells up to a tested
concentration of 2 mg/mL. Confocal microscopy results showed that
nanogel 1 delivered and released FITC–CC into
the perinuclei region of HeLa cells following 8 h incubation. CC-loaded
reductively degradable nanogels demonstrated apparently better apoptotic
activity than free CC as well as reduction-insensitive controls. These
in situ forming, surfactant and oil-free, and reduction-sensitive
degradable nanogels are highly promising for targeted protein therapy.