Abstract
For many decades, poly(2-oxazoline)s and poly(2-oxazine)s, two closely related families of polymers, have led the life of a rather obscure research topic with only a few research groups world-wide working with them. This has changed in the last five to ten years, presumably triggered significantly by very promising clinical trials of the first poly(2-oxazoline)-based drug conjugate. The huge chemical and structural toolbox poly(2-oxazoline)s and poly(2-oxazine)s has been extended very significantly in the last few years, but their potential still remains largely untapped. Here, specifically, the developments in macromolecular self-assemblies and non-covalent drug delivery systems such as polyplexes and drug nanoformulations based on poly(2-oxazoline)s and poly(2-oxazine)s are reviewed. This highly dynamic field benefits particularly from the extensive synthetic toolbox poly(2-oxazoline)s and poly(2-oxazine)s offer and also may have the largest potential for a further development. It is expected that the research dynamics will remain high in the next few years, particularly as more about the safety and therapeutic potential of poly(2-oxazoline)s and poly(2-oxazine)s is learned.
Highlights
Much work has been done in the field of thermoresponsive POx copolymers, where new architectures, such as gradient or star-shaped copolymers have been studied in a great detail, with respect to control over LCST, temperature driven self-assembly, crystallization, or gelation
While thermogelling POx were shown to be suitable candidates for bioinks or biomaterial inks for 3D printing, the application potential of other LCST copolymers or thermoresponsive stars or micelles remains more vague despite them being much more established in research
It will be interesting to see in which applications gradient copolymers can outperform or at least compete with block copolymers so that one can really benefit from the somewhat simpler preparation
Summary
The solubility of POx and POzi can be tuned by varying the length of the polymer side chain (Figure 1). Inspired by Pluronic thermogelling triblock copolymers, Zahoranová et al studied thermoresponsive behavior of ABA and BAB triblock copolymers composed of pMeOx and pPrOx with various ratios of the blocks and various chain lengths.[73] none of the prepared triblock copolymers exhibited thermogelation (as monitored by development of loss and storage moduli with increasing temperature), an increase of viscosity with temperature (thermothickening) was observed in some of the samples (Figure 4A), ABA copolymers with highest molecular masses (≈30 kg mol−1) These copolymers did not exhibit visible clouding, but rather temperature-induced self-assembly. This is connected with the fact that the mechanism behind the gelation of some particular types of block copolymers differs from standard model substances such as Pluronic F127 and needs to be clarified in more details
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