Synthesis of New Thermoresponsive Polymers Possessing the Dense 1,2,3-Triazole Backbone

Thermoresponsive water-soluble polymers, aqueous solutions of which undergo lower critical solution temperature (LCST)-type phase separation, have been investigated in detail for several decades. To develop LCST-type thermoresponsive polymers with new polymer backbone, 4-azido-5-hexynamide (AHA) derivatives were designed as monomers for copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC) polymerization. AHA derivatives carrying secondary amide side chains, that is, 4-azido-N-methyl-5-hexynamide (M), 4-azido-N-ethyl-5-hexynamide (E), and 4-azido-N-isopropyl-5-hexynamide (iP), were first synthesized and polymerized by CuAAC to obtain polymers (poly(M), poly(E), and poly(iP)). Contrary to our expectation, poly(M), poly(E), and poly(iP) were insoluble in water and many organic solvents presumably because of the formation of hydrogen bonding between the amide side chains or between the amide side chains and triazole residues in the backbone. Thus, AHA derivatives carrying tertiary amide side chains, that is, 4-azido-N,N-dimethyl-5-hexynamide (MM), 4-azido-N-ethyl-N-methyl-5-hexynamide (ME), 4-azido-N-isopropyl-N-methyl-5-hexynamide (MiP), and 4-azido-N,N-diethyl-5-hexynamide (EE), were also synthesized and polymerized to yield polymers (poly(MM), poly(ME), poly(MiP), and poly(EE)). These polymers were soluble in a number of common organic solvents. It is noteworthy that poly(MM) and poly(ME) were also soluble in water. The phase separation behavior of 1.0 wt % aqueous solutions of poly(MM) and poly(ME) was then investigated by transmittance measurements. These data indicated that poly(ME) was an LCST-type thermoresponsive polymer, whereas poly(MM) was not. A large hysteresis was observed in the transmittance measurements for the poly(ME) aqueous solution because of slow rehydration after phase separation. The phase separation behavior was investigated preliminarily by differential scanning calorimetry and ¹H NMR.

Multivalency Beats Complexity: A Study on the Cell Uptake of Carbohydrate Functionalized Nanocarriers to Dendritic Cells

Herein, we report the synthesis of carbohydrate and glycodendron structures for dendritic cell targeting, which were subsequently bound to hydroxyethyl starch (HES) nanocapsules prepared by the inverse miniemulsion technique. The uptake of the carbohydrate-functionalized HES nanocapsules into immature human dendritic cells (hDCs) revealed a strong dependence on the used carbohydrate. A multivalent mannose-terminated dendron was found to be far superior in uptake compared to the structurally more complex oligosaccharides used.

Preparation of a Series of Photoresponsive Polymersomes Bearing Photocleavable a 2-nitrobenzyl Group at the Hydrophobic/Hydrophilic Interfaces and Their Payload Releasing Behaviors

In this study, the structure-function relationships of a series of polymersomes composed of well-defined amphiphilic diblock copolymers were investigated. The building blocks were synthesized by clicking hydrophobic polymers, synthesized beforehand, and commercially available poly(ethylene glycol) with photocleavable 2-nitrobenzyl compounds bearing alkyne and maleimide functionalities. All of the tested polymersomes preserved their hollow structures even after sufficient photoirradiation. Nevertheless, the release rate of an entrapped anionic fluorophore was highly dependent on the molecular weight and the type of hydrophobic polymer, as well as on the presence or absence of the charged end groups. Moreover, the polymersomes with a 2-nitrosobenzyl photolysis residue within the hydrophobic shells exhibited photo-induced payload release after complete photolysis. It was concluded that the payload release was mediated by photo-induced permeability changes of the hydrophobic shells rather than the decomposition of their overall structures.