Ex Vivo and In Vitro Studies on the Cytotoxicity and Immunomodulative Properties of Poly(2‐isopropenyl‐2‐oxazoline) as a New Type of Biomedical Polymer

Abstract

Poly(2-alkenyl-2-oxazoline)s are promising functional polymers for a variety of biomedical applications, such as drug delivery systems, peptide conjugates, or gene delivery. In this study, poly(2-isopropenyl-2-oxazoline) (PIPOx) is prepared through free-radical polymerization initiated with azobisisobutyronitrile. Reactive 2-oxazoline units in the side chain support an addition reaction with different compounds containing a carboxylic group, which facilitates the preparation of polymers labeled with two different fluorescent dyes. The cytotoxicities of 2-oxazoline monomers, PIPOx, and fluorescently labeled PIPOx are evaluated in vitro using an 3-(4,5-Dimethyldiazol-2-yl)-2,5-diphenyl tetrazolium bromide assay and ex vivo using a cell proliferation assay with adenosine triphosphate bioluminescence. The cell uptake of labeled PIPOx is used to determine the colocalization of PIPOx with cell organelles that are part of the endocytic pathway. For the first time, it is shown that poly(2-isopropenyl-2-oxazoline) is a biocompatible material and is suitable for biomedical applications; further, its immunomodulative properties are evaluated.

ABA and BAB Triblock Copolymers Based on 2‐Methyl‐2‐oxazoline and 2‐n‐Propyl‐2‐oxazoline: Synthesis and Thermoresponsive Behavior in Water

“…One of the potential alternatives to polyethers such as PEG and Pluronics, in particular for medical applications, are poly(2‐alkyl‐2‐oxazoline)s (POx) . Poly(2‐ethyl‐2‐oxazoline) and poly(2‐methyl‐2‐oxazoline) were found nontoxic toward fibroblast cells up to concentrations of 10–20 g L −1 . Amphiphilic diblock and triblock copoly(2‐oxazolines) were shown to be nontoxic toward human breast cancer cells and canine kidney cells up to the concentrations 10 g L −1 .…”

Cytotoxicity of 2-oxazines and poly(2-oxazine)s in mouse fibroblast

“…10 g/L and 20 g/L, respectively. Compared to 2-oxazolines (MeOx, EtOx) the cytotoxicity of 2-oxazines is about one order of magnitude lower [23] . This may reflect the lower reactivity of the 2-oxazines compared to the 2-oxazolines.…”

Poly(2-isopropenyl-2-oxazoline) Hydrogels for Biomedical Applications

“…An important argument that moves PiPOx polymer forward to a variety of biological applications, is the recent report by Kronek's group concerning PiPOx's biocompatibility. 62 Consequently, we investigated the cytotoxic nature of PiPOx using MTT cytotoxicity assay to determine if there is any difference between the polymer obtained by radical (Kronek's study) and anionic polymerization (present study). The cytotoxicity studies revealed that the non-toxic concentration for a cell viability higher than 80% is 13.5 mg/mL after 24 h of incubation (Fig.…”

“…The results obtained are similar with those reported by Kronek. 62 Furthermore, we performed a cytotoxicity assay of the hydrogels to assess their use as potential biomaterials. For this test we used the hydrogel cross-linked with azelaic acid.…”

“…56 PiPOx is a versatile functional polymer as demonstrated in our recent reports 53,57,58 due to the following reasons: i) PiPOx is highly hydrophilic, ii) is chemically inert to moisture and oxygen during storage, iii) is a functional polymer which can be prepared with well-defined characteristics by several living and controlled polymerization techniques, 53,[59][60][61] iv) the ring opening addition of the oxazoline side-chain functionalities requires simple post-modification reaction conditions, 53, 57, 58 v) no catalysts are needed for the polymer analogous reaction, vi) no by-products are produced when reacted with carboxylic acids, 53,57,58,62 and vii) is biocompatible. 62 Even though these characteristics make PiPOx highly appealing for the development of hydrogels for biomedical applications, to date there are no reports regarding PiPOx's potential to be used as basis for the development of chemically cross-linked hydrogels. However, to ideally meet the requirements for usage in biomedical applications, in general, hydrogels need to: i) possess readily tunable hydrophilicity, ii) have a highly reproducible composition via synthesis (functionalization or cross-linking degree), iii) exhibit biocompatibility and degradability, whereas the degradation products should be non-toxic; and iv) should have good mechanical properties in order to be processed and manipulated.…”