Evaluation of the in vivo fate of ultrapure alginate in mice model

Abstract

Evaluation of the in vivo fate of ultrapure alginate in mice model Introduction: Alginate is an anionic co-polymer composed of (1, 4)-linked β-D-mannuronate (M) and α-L-guluronate (G) residues and is sourced from nature (eg. seaweed)[1]. This polymer has been comprehensively studied for use in various biomedical applications because of its reported biocompatibility, non-toxicity and mild gelation property[2],[3]. Mammals lack the enzyme alginase which is required for the biodegradation of the polymer chains of alginate[4]; however, thus far only one study has investigated the bio-distribution profile of radiolabeled chemically modified alginate (propylene glycol alginate-tyrosinamide)[2]. This study showed that the in vivo fate of modified alginate following systemic administration is dependent on the molecular weight and the higher molecular weight (> 48000 g/mol) alginate fragments remained in circulation with no significant accumulation in organs until 48 hours[3]. The lack of a bio-distribution study on pure alginate and of studies involving prolonged time points on the biodistribution profile of alginate-based polymers in general is a clear knowledge gap in the literature, as this information is crucial for alginate to be used in biomedical applications. Thus the present study which investigates the bio-distribution of cyanine 5-amine conjugated ultrapure alginate is highly topical. Materials and Methods: High purity alginate from FMC BioPolymer was conjugated with cyanine 5-amine using carbodiimide chemistry at a loading of 14 mg cyanine 5-amine/g alginate-dye conjugate. This polymer was administered to Balb/c mice through the tail vein, and imaged using a dual fluorescent X-ray imaging system (Bruker MsFx pro) at 1 hour, 2 hour, 1 day, and 2 days post sample administration under isoflurane anesthesia. At each time point, subsets of animals were euthanized and the organs (spleen, liver, heart, lungs, brain and kidney) were harvested for ex vivo imaging and flow cytometry analysis. Cyanine 5-amine was used as a control. Results and Discussion: From the imaging results at 1st hour, a rapid clearance of some of the alginate through the kidneys (e.g. smaller molecular weight alginate fragments) and liver (e.g. molecular weight alginate fragments) could be observed. Conclusion: The results of this in vivo biodistribution study will form the foundation for future research in the translation of alginate-based materials into different applications such as drug delivery, tissue engineering and wound healing. One of the authors A. Anitha is grateful to The University of Queensland, Australia for providing a postdoctoral research fellowship for carrying out this research work.