Acrylamide, Acrylic Acid and N-Isopropylacrylamide Hydrogels as Osmotic Tissue Expanders

Abstract

Background and Aim: Osmotically active tissue expanders allow the harvesting of soft tissue for reconstruction after different injuries. However, their expansion properties could be improved. Thus, our goal was to examine the in vivo applicability of acrylamide (AAm), acrylic acid (AAc) and N- isopropylacrylamide (NIPAAm) hydrogels. Materials and Methods: Cylinders of AAm, AAc and NIPAAm hydrogels were implanted under the skin of rats in the dorsal region. The diameter and the length of the cylinders were measured daily. After removal of the hydrogels, their mass and rheological properties were determined. Further, biopsies were taken from the adjacent tissue for histological analysis. Results: The hydrogels reached the peak of swelling by the end of the 2nd postoperative week. The wet mass of the removed cylinders was 25 times their dry mass prior to implantation. NIPAAm polymers exhibited the most favourable visco-elastic properties, with the highest tendency to retain their preformed shape. The histological analysis revealed serious tissue damage when the AAc devices were used, whereas the AAm and NIPAAm did not result in such lesions. Conclusion: In view of its mechanical and biological properties, NIPAAm hydrogel seems to be the most appropriate of these materials for application in plastic and reconstructive surgery.

Poly (Ethylene Glycol)‐Based Hydrogels as Self‐Inflating Tissue Expanders with Tunable Mechanical and Swelling Properties

“…Within days after placement of the tissue expanders, a new network of vessels developed as can be observed in Figure B(II),C(II). An ideal tissue expander should retain its shape upon implantation and during the explantation phase . After explantation, both P6 and P8 expanders showed considerable swelling ratio while retaining their original shapes (Figure B(III),C(III)).…”

“…In addition, physical restrictions of the device may prevent its use in some anatomical locations (e.g., craniofacial or cleft palate surgery) . Hence, development of a new generation of tissue expanders may be useful in order to eliminate these limitations …”

Biodegradable Elastic Hydrogels for Tissue Expander Application

“…In this case, the role of a gel to act as a pressuregenerating device is based on the balancing of the osmotic pressure and the rubber elasticity. If the swelling pressure can overcome the resistance of the adjacent tissue, it is suffi cient to dilate the surrounding tissue at the expected rate [37] . Previous research has established that a pressure close to 100 mmHg is ideal for tissue expansion [38] .…”

“…The hydrogel achieved a 25 -fold increase in mass. NIPAAm polymers exhibited the most favorable viscoelastic properties, with the highest tendency to retain their preformed shape [37] . Thus, NPIAAm hydrogels allow the acquisition of more skin for reconstructive interventions.…”

Compressive moduli and network parameters of N‐isopropylacrylamide hydrogels copolymerized by monoesters of itaconic acid and crosslinked with tetraallylammonium bromide

“…Because of their high water content, the hydrogels have flexible structures, being very similar to that of tissues, but the low tensile or compression strengths limit their use in biological applications. The formation of hydrophobically modified copolymers, double networks, and nanocomposite gels by the addition of hydrophobic components and inorganic layered structures, respectively, into the hydrogel compositions can be given as the main examples of the methods that are used to improve the mechanical properties …”