Targeting of antigens to dendritic cells (DCs) to induce strong cellular immune response can be established by loading in a nano‐sized carrier and keeping the antigen associated with the particles until they are internalized by DCs. In the present study, a model antigen (ovalbumin, OVA) is immobilized in cationic dextran nanogels via disulfide bonds. These bonds are stable in the extracellular environment but are reduced in the cytosol of DCs due to the presence of glutathione. Reversible immobilization of OVA in the nanogels is demonstrated by the fact that hardly any release of the protein occurred at pH 7 in the absence of glutathione, whereas rapid release of OVA occurs once the nanogels are incubated in buffer with glutathione. Furthermore, these OVA conjugated nanogels show intracellular release of the antigen in DCs and boost the MHC class I antigen presentation, demonstrating the feasibility of this concept for the aimed intracellular antigen delivery.
In this study, native
chemical ligation (NCL) was used as a selective
cross-linking method to form core-cross-linked thermosensitive polymeric
micelles for drug delivery applications. To this end, two complementary
ABA triblock copolymers having polyethylene glycol (PEG) as midblock
were synthesized by atom transfer radical polymerization (ATRP). The
thermosensitive poly isopropylacrylamide (PNIPAM) outer blocks of
the polymers were copolymerized with either N-(2-hydroxypropyl)methacrylamide-cysteine
(HPMA-Cys), P(NIPAM-co-HPMA-Cys)-PEG-P(NIPAM-co-HPMA-Cys) (PNC) or N-(2-hydroxypropyl)methacrylamide-ethylthioglycolate
succinic acid (HPMA-ETSA), P(NIPAM-co-HPMA-ETSA)-PEG-P(NIPAM-co-HPMA-ETSA) (PNE). Mixing of these polymers in aqueous
solution followed by heating to 50 °C resulted in the formation
of thermosensitive flower-like micelles. Subsequently, native chemical
ligation in the core of micelles resulted in stabilization of the
micelles with a Z-average of 65 nm at body temperature.
Decreasing the temperature to 10 °C only affected the size of
the micelles (increased to 90 nm) but hardly affected the polydispersity
index (PDI) and aggregation number (Nagg) confirming covalent stabilization of the micelles
by NCL. CryoTEM images showed micelles with an uniform spherical shape
and dark patches close to the corona of micelles were observed in
the tomographic view. The dark patches represent more dense areas
in the micelles which coincide with the higher content of HPMA-Cys/ETSA
close to the PEG chain revealed by the polymerization kinetics study.
Notably, this cross-linking method provides the possibility for conjugation
of functional molecules either by using the thiol moieties still present
after NCL or by simply adjusting the molar ratio between the polymers
(resulting in excess cysteine or thioester moieties) during micelle
formation. Furthermore, in vitro cell experiments demonstrated that
fluorescently labeled micelles were successfully taken up by HeLa
cells while cell viability remained high even at high micelle concentrations.
These results demonstrate the potential of these micelles for drug
delivery applications.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.