Transient Multivalent Nanobody Targeting to CD206-Expressing Cells via PH-Degradable Nanogels.

To target nanomedicines to specific cells, especially of the immune system, nanobodies can be considered as an attractive tool, as they lack the Fc part as compared to traditional antibodies and, thus, prevent unfavorable Fc-receptor mediated mistargeting. For that purpose, we have site-specifically conjugated CD206/MMR-targeting nanobodies to three types of dye-labeled nanogel derivatives: non-degradable nanogels, acid-degradable nanogels (with ketal crosslinks), and single polymer chains (also obtained after nanogel degradation). All of them can be obtained from the same reactive ester precursor block copolymer. After incubation with naïve or MMR-expressing Chinese hamster ovary (CHO) cells, a nanobody mediated targeting and uptake could be confirmed for the nanobody-modified nanocarriers. Thereby, the intact nanogels that display nanobodies on their surface in a multivalent way showed a much stronger binding and uptake compared to the soluble polymers. Based on their acidic pH-responsive degradation potential, ketal crosslinked nanogels are capable of mediating a transient targeting that gets diminished upon unfolding into single polymer chains after endosomal acidification. Such control over particle integrity and targeting performance can be considered as highly attractive for safe and controllable immunodrug delivery purposes.

Poly(2-methyl-2-oxazoline) conjugates with doxorubicin: From synthesis of high drug loading water-soluble constructs to in vitro anti-cancer properties.

Poly(2-oxazoline)s represent an emerging class of polymers with increasing potential in biomedical sciences. To date, most of the work on poly(2-oxazoline)-drug conjugates focused on poly(2-ethyl-2-oxazoline) (PEtOx), a biocompatible water-soluble polymer with biological properties similar to polyethylene glycol. However, the more hydrophilic poly(2-methyl-2-oxazoline) (PMeOx) shows better anti-fouling properties than PEtOx and thus indicates greater potential for the construction of polymer therapeutics. Herein, we synthesized for the first time a drug delivery system based on a linear PMeOx with a molar mass that is high enough (40 kDa) to exploit passive accumulation in the tumor by the enhanced permeation and retention effect. The anti-cancer drug doxorubicin is attached to the polymer carrier via an acid-sensitive hydrazone bond, which allows its pH-triggered release in the tumor. The in vitro study demonstrates successful cellular uptake of the PMeOx-doxorubicin conjugate via clathrin-mediated endocytosis, pH-sensitive drug release and high cytotoxicity against B16 melanoma cells. Finally, these properties were critically compared to the analogous systems based on the established PEtOx revealing that the more hydrophilic PMeOx carrier outperforms PEtOx in most of the parameters, showing higher maximal drug loading, superior cellular uptake, better anti-fouling properties, as well as improved in vitro anti-cancer efficiency. The study demonstrates the potential of PMeOx as a versatile platform for synthesis of new drug delivery systems.

Transiently Responsive Block Copolymer Micelles Based on N-(2-Hydroxypropyl)methacrylamide Engineered with Hydrolyzable Ethylcarbonate Side Chains.

The lack of selectivity and low solubility of many chemotherapeutics impels the development of different biocompatible nanosized drug carriers. Amphiphilic block copolymers, composed of a hydrophilic and hydrophobic domain, show great potential because of their small size, large solubilizing power and loading capacity. In this paper, we introduce a new class of degradable temperature-responsive block copolymers based on the modification of N-(2-hydroxypropyl)methacrylamide (HPMA) with an ethyl group via a hydrolytically sensitive carbonate ester, polymerized by radical polymerization using a PEG-based macroinitiatior. The micellization and temperature-responsive behavior of the PEG-poly(HPMA-EC) block copolymer were investigated by dynamic light scattering (DLS). We observed that the polymer exhibits lower critical solution temperature (LCST) behavior and that above the cloud point (cp) of 17 °C the block copolymer self-assembles in micelles with a diameter of 40 nm. Flow cytometry analysis and confocal microscopy show a dose-dependent cellular uptake of the micelles loaded with a hydrophobic dye. The block copolymer nanoparticles were capable of delivering the hydrophobic payload into cancer cells in both 2D and 3D in vitro cultures. The block copolymer has excellent cytocompatibility, whereas loading the particles with the hydrophobic anticancer drug paclitaxel results in a dose-dependent decrease in cell viability.