pH-Responsive, Thermo-Resistant Poly(Acrylic Acid)-g-Poly(boc-L-Lysine) Hydrogel with Shear-Induced Injectability

Abstract

In this study we report the rheological behavior of aqueous solutions of an amphiphilic graft copolymer constituting a polyacrylic acid (PAA) grafted by poly(boc-L-lysine), P(b-LL). Due to the highly hydrophobic nature of the grafted chains, the copolymer self-assembles spontaneously in aqueous media forming three-dimensional (3D) finite size networks (microgels). The rheological analysis demonstrated that the copolymer behaves as a strong elastic hydrogel, showing characteristics of a “frozen” network. Moreover, it is noteworthy that the formulation shows the above-described characteristics in very small concentrations (0.25–1.20 wt%) compared to other naturally cross-linked hydrogels that have been studied so far. Concentration significantly affects the rheological properties of the hydrogel, showing considerable increase in elastic modulus, following the scaling law G’~C1.93. At the same time, the hydrogels can be described as intelligent stimuli-responsive systems, showing pH and shear responsiveness as well as stability with temperature changes. Thanks to the pH dependance of the degree of ionization of the weak polyelectrolyte PAA backbone, stiffness and swelling of the hydrogels can be tuned effectively by adjusting the pH conditions. Simulating conditions such as those of injection through a 28-gauge syringe needle, the gel demonstrates excellent response to shear, due to its remarkable shear thinning behavior. The combination of pH-sensitivity and shear responsiveness leads to excellent injectability and self-healing properties, given that it flows easily upon applying a low stress and recovers instantly in the site of injection. Therefore, the physically cross-linked PAA-g-P(b-LL) hydrogel exhibits remarkable features, namely biocompatibility, biodegradability of cross-links, pH responsiveness, shear-induced injectability and instantaneous self-healing, making it a potential candidate for various biomedical applications.

Comprehensive analysis of cationic dye removal from synthetic and industrial wastewater using a semi-natural curcumin grafted biochar/poly acrylic acid composite hydrogel

“…Absence of crossover frequency shows the permanent chemical crosslinking in the structure of the hydrogel. 66,67…”

pH-Sensitive Poly(acrylic acid)-g-poly(L-lysine) Charge-Driven Self-Assembling Hydrogels with 3D-Printability and Self-Healing Properties

“…PAA-g-P(boc-LL) graft copolymer (bearing boc-protected -NH 2 ) was synthesized by the grafting onto method using carbodiimide chemistry. Details about this process are reported elsewhere [35]. The graft copolymer molecular characteristics are M w = 575,202 Da and grafting density 8% mol (that is, 11 PLL side chains per backbone).…”

“…More importantly, the hydrogel exhibits shear-induced 3D printability and self-healing properties. Worthy noted that the precursor graft copolymer bearing the same number of grafted hydrophobic poly(boc-LL) (PAA-g-P(boc-LL)) forming hydrophobically crosslinked hydrogels were recently reported [35]. Thus, it gives us the opportunity to discuss the effect of different association modes (ionic vs. hydrophobic interactions) on the structure and mechanical response of the two hydrogel formulations.…”

Hydrogel nanoparticles as new drug delivery system for CNS disorders

“…It has been discovered that polyethylene glycol (PEG) and polyacrylamide (PAM)-based hydrogels containing polyacrylamide PAM are excellent for regenerating brain tissue. [98] Self-assembling hydrogels, composed of proteins combined with natural, synthetic, or hybrid hydrogels, have potential use in CNS tissue engineering. The hydrogel, which is based on the Ile-Lys-Val-Ala-Val (IKVAV) sequence, facilitates the formation of threedimensional networks and promotes the differentiation of neural stem cells (NSCs) into neurons.…”

“…Materials like hydrogels are crucial for CNS regeneration. It has been discovered that polyethylene glycol (PEG) and polyacrylamide (PAM)‐based hydrogels containing polyacrylamide PAM are excellent for regenerating brain tissue [98] . Self‐assembling hydrogels, composed of proteins combined with natural, synthetic, or hybrid hydrogels, have potential use in CNS tissue engineering.…”