Rheology as a Powerful Tool in Tunning Mechanical Properties of Nanocomposites

Hydrogels and nanoparticles (NPs), whether used separately or in combination, offer versatile platforms for nanotheranostics. The hydrogel provides a smart platform for drug delivery with controlled and targeted release of the therapeutic agent, additionally enabling combinatory therapies to address complex diseases. NPs have excelled as drug delivery carriers by encapsulating small molecules, peptides, proteins, and nucleic acids, being more versatile and carrying higher payloads than conventional drug delivery systems. The uniform distribution of NPs within a hydrogel matrix is crucial for applications such as drug delivery, tissue engineering, and sensing, as it ensures consistent and predictable material properties and performance [1-4]. In this work, we present a hydrogel system with four components: the GelMA (gelatine methacryloyl) as the main matrix, PAMAM (Poly(amidoamine) as vectors for nucleic acids, and finally gold nanoparticles (AuNPs) as photothermal agents. To further optimize and facilitate the design of the hydrogel, rheology was used to provide valuable insights into the structure, properties, and performance of the hydrogel with NPs, as well as sensitivity to temperature. Rheology was used to characterise the mechanical properties of the hydrogels under steady shear flow and oscillating flow, allowing the optimisation of the system formulation, as well as the injectable parameters. Namely, viscosity curves were estimated at different temperatures. The dynamical spectrum was evaluated through the moduli G' and G '' in the LVR regime and temperature ramps allowed the estimation of the gelation temperature. UV-light was used to promote in-situ crosslink of the hydrogels, after which the mechanical properties were evaluated showing significant improvements.