Nanoallotrope-integrated polyacrylamide hydrogels: a synergistic experiment–theory approach for engineering mechanically resilient and cytocompatible composites for cartilage tissue regeneration

Polyacrylamide (PAM)-based hydrogels are commonly acknowledged as promising contenders for replacing cartilage. Nevertheless, their restricted mechanical strength and puncture resistance greatly impeded their ability to be used in biological applications. The current investigation aimed to increase the strength of polyacrylamide hydrogels by including carbon nanotubes (CNTs) and graphene oxide (GO) in various concentrations in a PAM matrix. Combining CNT and GO nanoparticles with PAM results in a synergistic effect and a strong interfacial bonding. This leads to high compressive strength and elastic modulus. The PAM-CNT and PAM-GO composite hydrogels exhibited remarkable self-healing characteristics, bioactivity, and cytocompatibility. This was evidenced by a cell survival rate of over 99%. The incorporation of GO markedly improved the hydrophilicity of the composites, resulting in a contact angle of 40°. The swelling characteristics of the hydrogels were assessed, revealing that PAM-GO1 (0.3 g L^-1) and PAM-GO2 (0.5 g L^-1) exhibited the greatest stability. In vitro degradation tests showed that both PAM-GO1 (0.3 g L^-1) and PAM-GO2 (0.5 g L^-1) preserved approximately 90% of their gel mass following 20 days of immersion in PBS. Compression tests revealed that PAM-GO1 (0.3 g L^-1) has the greatest compressive strength (≈0.31 MPa) and highest elastic modulus (1.653 MPa). Furthermore, the PAM-GO hydrogels demonstrated exceptional cell survival, almost surpassing 100%. The best antimicrobial activity was found in PAM-GO1. In attaining new insights into the structural [interfacial interactions recognized by the noncovalent interactions (NCIs) and van der Waals (vdW) interactions], stability/strength, energetic [binding energy (BE)], and electronic [HOMO-LUMO gap and charge transfer (CT)] features of both composites, an in-silico approach has been applied. The PAM-GO composite model was found to be more stable than the PAM-CNTCOOH composite model. The BE, HOMO-LUMO gap, some selected QTAIM-based parameters, dipole moment, and CT-related parameters supported the experiment-based outcomes. In summary, the PAM-GO1 (0.3 g L^-1) hydrogel composite, characterized by enhanced mechanical characteristics, bioactivity, and robust adhesion, has considerable potential as an advanced hydrogel material for cartilage repair applications.