Alkyl Chain-Grafted Poly(l‑lysine) Vesicles with Tunable Molecular Assembly and Membrane Permeability

The preparation of alkyl chain-grafted poly­(l-lysine) (PLL) vesicles with tunable molecular assembly in aqueous solution and the evaluation of their membrane permeability by drug release experiments have been investigated. Upon grafting long alkyl chains, polypeptides confined in the assembled nanostructures adopted ordered conformations such as α-helices or β-sheets/turns, leading to the dense packing of membranes and, consequently, the decreases in vesicular size and membrane permeability. The vesicles can also be cross-linked by genipin to form stable structures with tunable membrane permeability. Additionally, these vesicles exhibited noticeable pH-sensitive behavior, depending on the grafted alkyl chain and cross-linking

Dual Stimuli-Responsive Polymeric Hollow Nanogels Designed as Carriers for Intracellular Triggered Drug Release

Dual stimuli-responsive hollow nanogel spheres serving as an efficient intracellular drug delivery platform were obtained from the spontaneous coassociation of two graft copolymers into the vesicle architecture in aqueous phase. Both copolymers comprise acrylic acid (AAc) and 2-methacryloylethyl acrylate (MEA) units as the backbone and either poly­(<i>N</i>-isopropylacrylamide) (PNIPAAm) alone or both PNIPAAm and monomethoxypoly­(ethylene glycol) (mPEG) chain segments as the grafts. The assemblies were then subjected to covalent stabilization within vesicle walls with ester-containing cross-links by radical polymerization of MEA moieties, thereby leading to hollow nanogel particles. Taking the advantage of retaining a low quantity of payload within polymer layer-enclosed aqueous chambers through the entire loading process, doxorubicin (DOX) in the external bulk phase can be effectively transported into the gel membrane and bound therein via electrostatic interactions with ionized AAc residues and hydrogen-bond pairings with PNIPAAm grafts at pH 7.4. With the environmental pH being reduced (e.g., from 7.4 to 5.0) at 37 °C, the extensive disruption of AAc/DOX complexes due to the reduced ionization of AAc residues within the gel layer and the pronounced shrinkage of nanogels enable the rapid release of DOX species from drug-loaded hollow nanogels. By contrast, the drug liberation at 4 °C was severally restricted, particularly at pH 7.4 at which the DOX molecules remain strongly bound with ionized AAc residues and PNIPAAm grafts. The in vitro characterizations suggest that the DOX-loaded hollow nanogel particles after being internalized by HeLa cells via endocytosis can rapidly release the payload within acidic endosomes or lysosomes. This will then lead to significant drug accumulation in nuclei (within 1 h) and a cytotoxic effect comparable to free drug. This work demonstrates that the novel DOX-loaded hollow nanogel particles show great promise of therapeutic efficacy for potential anticancer treatment

pH-dependent characteristics of DOX-loaded GCPVs and DOX-loaded chitosan/ poly(γ-GA)-deposited polymeric vesicles.

<p>(a) DLS colloidal particle size distribution profiles of DOX-loaded GCPVs in aqueous media of various pH. (b) Zeta potentials of DOX-loaded GCPVs and DOX-loaded chitosan/ poly(γ-GA)-deposited polymeric vesicles in different pH aqueous media.</p

Flow cytometric histogram profiles of HeLa cells incubated with free DOX, DOX-loaded vesicles and DOX-loaded GCPV.

<p>DOX fluorescence intensity of HeLa cells incubated with free DOX (red), DOX-loaded vesicles (green) and DOX-loaded GCPV (blue) at 37°C for 1 and 2 h, respectively. Untreated cells (black) were used as a control.</p

Recipes, compositions and average molecular weights of the derived polypeptide adducts.

a<p>Determined by ¹H-NMR in DMSO-<i>d₆</i> at 20°C.</p>b<p>Obtained by theoretical calculation as follows: poly(γ-GA) M_w 15600 (g/mol) + number of conjugated distearin moieties × 625 (M_w of distearin)</p>c<p>Obtained by theoretical calculation as follows: poly(γ-GA) M_w 15600 (g/mol) + number of conjugated Osu moieties ×114 (M_w of OSu) + number of mPEG grafts ×5000 (M_w of mPEG).</p

¹H-NMR spectra of (a) poly(γ-GA-co-γ-DSGA) and (b) poly(γ-GA-co-γ-GAOSu)-g-mPEG in DMSO-<i>d₆</i> at 25°C.

<p>¹H-NMR spectra of (a) poly(γ-GA-co-γ-DSGA) and (b) poly(γ-GA-co-γ-GAOSu)-g-mPEG in DMSO-<i>d₆</i> at 25°C.</p

Angle-dependent DLS/SLS data and TEM images of lipid/polypeptide conjugate vesicles (a, b) and DOX-loaded GCPVs (c, d).

<p>Angle-dependent DLS/SLS data and TEM images of lipid/polypeptide conjugate vesicles (a, b) and DOX-loaded GCPVs (c, d).</p

D_h, PSD and zeta potential of the polymeric vesicles, DOX-loaded vesicles, DOX-loaded chitosan-caged vesicles and DOX-loaded GCPVs in aqueous solutions at 25°C.

a<p>Determined by DLS (Malvern Zetasizer Nano-ZS instrument) at a scattering angle of 173^o, using the cumulant analysis method.</p

Schematic illustration of the development of DOX-loaded GCPVs and their pH-triggered drug release.

<p>Schematic illustration of the development of DOX-loaded GCPVs and their pH-triggered drug release.</p

Synthetic route of (a) poly(γ-GA-co-γ-DSGA) and (b) poly(γ-GA-co-γ-GAOSu)-g-mPEG.

<p>Synthetic route of (a) poly(γ-GA-co-γ-DSGA) and (b) poly(γ-GA-co-γ-GAOSu)-g-mPEG.</p