## 4 Discussion  
Cell-based therapy has been recognized as a next-generation therapeutic method because of the excellent therapeutic effects it delivers, but it has serious issues in therapeutic application including low cell survival after transplantation, adverse effects, high cost, and heterogeneous quality [1,28]. Recent studies have successfully addressed these issues by designing or functionalizing cells. The cell sheet technique is one of the well-known cell functionalization methods, which has been applied to some cellular drugs used in clinical applications. In addition, a three-dimensional cell sheet construction method and a vascular network structure formation method have been developed and have improved the therapeutic usefulness of the cell sheets [29]. Second, a three-dimensional cell culture such as cell spheroids is also useful. As with the cell sheet method, this method can realize a strong intercellular interaction in the cell aggregates, causing the improvement of cellular function and cell survival after transplantation [30]. Third, gene transferring to cells has dramatically changed cell-based therapy, and a typical example is chimeric antigen receptor (CAR) T cells therapy [31]. Since the expression of functional proteins in living cells by gene transferring can overcome several issues in cell-based therapy, genetically modified cellular drugs will be increasingly developed. In addition, cell capsulation, hydrogel, cell surface modification, and mitochondria transferring have shown their usefulness in cell-based therapy. These methods are essential to maximize the therapeutic effects of cell-based therapy with safety, and functionalized or designed cellular drugs will be developed by using these methods. Cell encapsulation is an excellent method for cell-based therapy, and various materials have been employed for encapsulation [32]. Although agarose, hyaluronic acid, gelatin, fibrin, and other materials have been used for encapsulation, they differ in terms of their origin, mode of gelation, and biodegradability [33]. Among these, sodium alginate is the most commonly used owing to its availability, low cost, and ease of fabrication. Hydrogels consisting of collagen, chitosan, or agarose are frequently used; however, achieving optimal cell internalization with these agents can be challenging, thus restricting their application [34]. Recently, chemically modified alginic acid has been developed and was found to  
Figure 5: Survival and therapeutic effect of encapsulated cells after transplantation into mice. (**a**) Ten alginate capsules containing C3H10T1/2/Nluc cells at 5 \(\times\) 10\({}^{3}\) cells/capsule were intraperitoneallyally transplanted in BALB/c-nu/nu mice. In addition, 5 \(\times\) 10\({}^{4}\) suspended C3H10T1/2/Nluc cells were intraperitoneallyally transplanted. Relative light units in blood were measured. Results are expressed as the mean \(\pm\) standard deviation (SD) (\(n\) = 4–6). The level of significance was measured using Student’s \(t\)-test compared to the suspended cell group (* \(p\) < 0.05). (**b**) Fifteen alginate capsules containing 5 \(\times\) 10\({}^{4}\) MIN6 cells were intraperitoneallyally transplanted to C57 BL/6 diabetic mice. Suspended MIN6 cells were intraperitoneallyally transplanted at a level of 7.5 \(\times\) 10\({}^{5}\) cells. Blood glucose levels were measured. Results are expressed as the mean \(\pm\) SD (\(n\) = 4–9). The level of significance was measured using ANOVA following [PERSON]’s test compared to the sham-treated group (* \(p\) < 0.05). inhibic capsule fibrosis after transplantation. These alignates, which are strong polyanions, neither adhere to cells nor activate an immune response, while cationic materials tend to induce inflammatory responses [35]. Alginate gels are obtained when sodium alginate solution is slowly dropped into a calcium chloride solution in physiological conditions.