Several groups have extensively studied several natural and synthetic polymers with the goal of developing the most suitable biomaterial for cell microencapsulation. Extensive work has been done using alginates which are regarded as the most suitable biomaterials for cell microencapsulation due to their abundance, excellent biocompatibility and  biodegradability properties. Alginate is a natural polymer which can be extracted from seaweed and bacteria with numerous compositions based on the isolation source.
Alginate is not free from all criticism. Some researchers believe that alginates with high-M content could produce an inflammatory response and an abnormal cell growth while some have demonstrated that alginate with high-G content lead to an even higher cell overgrowth and inflammatory reaction in vivo as compared to intermediate-G alginates.
Even ultrapure alginates may contain endotoxins, and polyphenols which could compromise the biocompatibility of the resultant cell microcapsules. It has been shown that even though purification processes successfully lower endotoxin and polyphenol content in the processed alginate, it is difficult to lower the protein content and the purification processes could in turn modify the properties of the biomaterial. Thus it is essential that an effective purification process is designed so as to remove all the contaminants from alginate before it can be successfully used in clinical applications.