Page 407 - IJB-9-6

International Journal of Bioprinting Biofabrication for islet transplantation

PLGA-porous microspheres upregulated the expression strategy for encapsulating transplanted islets using a
of vascular-related genes, indicating their potential conformal coating (CC) technique with PEG hydrogels .
[67]
to promote vascular formation during artificial organ This method produces hydrogel CCs that encompass
construction using PLGA-porous microspheres . the islets at physiological pH, thereby promoting
[58]
Polylactic acid (PLA) is an aliphatic polyester that cytocompatibility and scalability. To evaluate the efficacy
degrades through hydrolysis. It exhibits desirable and efficiency of this novel method, in vitro and in vivo
characteristics such as biocompatibility, degradability, experiments were conducted using various small and large
and printability, making it a popular choice for use as a animal models of T1D (Figure 3E). During the evaluation
polymeric bioink . The incorporation of PLA allows of dynamic glucose-stimulated insulin secretion, both
[59]
for the facile production of porous scaffolds that can naked and emulsion-coated human islets exhibited a
effectively promote the growth of neotissues. To date, a characteristic perifusion profile characterized by an initial
diverse array of medical products has been developed phase of insulin secretion reaching its peak, followed by
utilizing PLA, including degradable constructs and a subsequent phase wherein insulin secretion plateaued
[60]
porous scaffolds for tissue engineering applications . during the high-glucose stimulus (Figure 3F). The results
Huang et al. presented an innovative co-transplantation revealed improved biocompatibility and abundant graft
[67]
system that employed nanocomposite microgels loaded revascularization (Figure 3G) . Another distinguishing
with islets and was capable of a sustained in situ release of feature of PEG is its potential to be modified with specific
immunosuppressants in conjunction with biodegradable ligands to promote tissue adhesion. This property permits
oxygen-generating microspheres (Figure 3C) . In their targeted cell attachment and proliferation, which is highly
[61]
study, PLA was selected as the microsphere packaging advantageous in tissue engineering applications, where
material because of its biodegradability. Co-transplantation successful regeneration hinges on cell adhesion. Despite
of nanocomposite microgels and biodegradable their usefulness, the biocompatibility of hydrophobic
microspheres into diabetic mice restored and maintained materials is restricted by their inherent nature, and the
normoglycemia (Figure 3D) . Hoveizi and Tavakol breakdown of these materials can release acidic byproducts
[61]
[68]
successfully engineered a dependable 3D differentiation with proinflammatory effects . Furthermore, several
methodology for mesenchymal stem cells (MSCs) into synthetic materials employed in tissue engineering,
pancreatic beta cell precursors (PBCPs) using nanofibrous including PEG, are non-biodegradable and may remain
PLA scaffolds . The biocompatible and biodegradable indefinitely in the body, possibly causing unfavorable
[62]
nature of the nanofibrous PLA scaffold provided a suitable reactions or necessitating surgical removal.
biophysical microenvironment for MSCs. Remarkably, 3.4. Decellularized tissue-driven ECM
transplanted PBCPs have demonstrated the ability to Tissue decellularization refers to the removal of cellular
ameliorate hyperglycemia in a murine diabetes-induced components from a tissue or solid organ, resulting
model . However, the degradation of PLA generates in an acellular 3D structure composed of the ECM.
[62]
acidic byproducts, which negatively impact its long-term Decellularized extracellular matrix (dECM) exhibits
biocompatibility by triggering tissue inflammation and non-toxicity toward the proliferation and differentiation
cellular death. of various cell types, indicating its potential utility in
Polyethylene glycol (PEG) has emerged as a promising regenerative medicine. Recent research on tissue-specific
material for islet encapsulation owing to its tunable dECM has effectively provided a vital microenvironment
properties and gelation ability, which facilitate crosslinking for cells, allowing for the modulation of cellular
and photopolymerization [63,64] . Several studies have processes such as migration, differentiation, and function
demonstrated the ability of PEG to encapsulate thinner during tissue morphogenesis [69,70] . The pancreatic
islets. For instance, a thin layer-by-layer PEG approach dECM, comprising collagen, laminin, fibronectin, and
was utilized in one study to create an ultrathin capsule fibrin, plays a crucial role in cytoskeletal remodeling,
for surrounding the islets, which significantly enhanced contractility, and cell differentiation. The dECM of
the molecular exchange across the membrane compared the pancreas offers significant advantages, such as
with earlier methods . Weaver et al. incorporated biocompatibility and bioactivity, which can increase islet
[65]
PEG hydrogel into a macroencapsulation device for survival and decrease cytotoxicity, thereby enhancing
extrahepatic islet transplantation . The device comprises islet function. Research focusing on dECM derived
[66]
a hydrogel core crosslinked with non-degradable PEG from pancreatic tissue has validated its characteristics,
dithiol and an outer layer that is vasculogenic and especially regarding the interactions between islets and
crosslinked with a proteolytically sensitive peptide to environmental cues, including viability, insulin secretion,
stimulate degradation . Stock et al. introduced a refined and glucose responsiveness (Table 1) .
[71]
[66]
Volume 9 Issue 6 (2023) 399 https://doi.org/10.36922/ijb.1024