**4. Conclusion**

*Nano- and Microencapsulation - Techniques and Applications*

Barium alginate Various duration for

Alginate high in guluronic acid

Ultrapure alginate (68% glucuronic acid)

poly-l-ornithine-sodium

Ultra-purified sodium

Ultrapure-low viscosity high guluronic acid-rich

alginate

**Table 1.**

Alginate-Poly-L-Ornithine

alginate

alginate

popular level between 2010 and 2012 [54]. For the last 2 years, researchers provided detailed *in vivo* experiments and defined an alginate encapsulation strategy in a more enhanced way [52, 60, 70, 71] . The vast majority of attempts have been made to treat T1DM and the critical requirements remain to be elucidated in the future. Another endocrine replacement therapy performed for hypoparathyroidism by encapsulated parathyroid tissue/cell transplantation (PTX) was described only in seven case reports for 12 recipients [43, 56, 67–69, 72, 73] between 1997 and 2019. Six of these case studies used alginate for encapsulation. In 1997, Hasse et al. performed the first microencapsulated PTX for two recipients and reported 3 months of graft survival [72]. The second one, performed by Zimmerman et al. in 2001 for one recipient showed no trace of parathyroid tissue particles nor microcapsules, after 3 months, from histological samples from the implantation site of the recipient [43]. The third transplantation case reported up to 1 year graft survival by Tibell et al. and they had macroencapsulated the parathyroid tissue particles and transplanted into four recipients [67]. Another case by Ulrich et al. reported two PTX recipients had elevations in PTH levels and reduced the supplementation requirement into half dose [68]. In 2009, Cabane et al. microencapsulated the enzymatically isolated parathyroid cells in one recipient and reported the longest follow-up data with 20 months of graft survival [69]. The last and seventh case performed by Yucesan et al. in 2019 microencapsulated parathyroid cell transplantation for one recipient reported and the results followed for a year with success [56]. Despite these achievements, the necessity of immunoisolation for parathyroid allotransplantation requires more case studies with long-term

Collagen/Alginate n/a Beta-cells (Islets) 2010 [65] Sodium alginate 3 months Parathyroid cells 1997 [66] Amitogenic alginate <3 months Parathyroid cells 2001 [43]

n/a n/a Parathyroid cells 2004 [68] Sodium alginate <20 months Parathyroid cells 2009 [69]

**Alginate type Graft survival Graft Year Reference**

four recipients

n/a 1 year Parathyroid tissue

*Some of the examples of alginate derivates used in microencapsulation studies.*

9 months Beta-cells (Islets) 1994 [49]

3 months Beta-cells (Islets) 2013 [50]

<1 year Beta-cells (Islets) 2006 [62]

3 years Beta-cells (Islets) 2011 [63]

<8 months Beta-cells (Islets) 2010 [64]

particles

>1 year Parathyroid cells 2019 [56]

Beta-cells (Islets) 2009 [51]

2001 [67]

**174**

follow-up data.

Immunoisolating construct tuning may be achieved by defining the mechanical properties, molecular weight, cross-linking density of the polymer, and the concentration balance between the therapeutic graft/drug and the biomaterial. These proportions still require optimal decisions even with the known performances of encapsulated cells.

Significant efforts have been made so far by ongoing studies from research laboratories and biotechnology companies, which continue to encounter microencapsulation strategies at every step. The future perspective is strong enough to overcome the current limitations. Nevertheless, alginate is the best natural product to be used by many different disciplines at the same time.

### **Conflict of interest**

The authors declare no conflict of interest.

#### **Author details**

Beyza Goncu1 \* and Emrah Yucesan<sup>2</sup>

1 Experimental Research Center, Bezmialem Vakif University, Istanbul, Turkey

2 Department of Medical Biology, Faculty of Medicine, Bezmialem Vakif University, Istanbul, Turkey

\*Address all correspondence to: bsgoncu@gmail.com; bgoncu@bezmialem.edu.tr

© 2020 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
