Cowman and colleagues have previously shown that native HA is composed of long and thin strands with diameters of around 0.5 nm and can appear in several different conformations. In the HYA and NP0 or NP5000 co-treated samples, the appearance of mesh-like aggregates was observed, while no such patterns were visible after PLGA NP treatments. NP0-mediated aggregates resulted in larger structures compared to the less positive NP5000 suggesting the role of charge-dependent biomolecule adsorption. In ADA-stimulated explant supernatants, a distinct branched structure of ACAN with a thickness of about 10 nm was observed, in agreement with reports by Ng et al. Co-treatment with NPs resulted instead in the formation of small round aggregates. In addition, mesh-like structures were observed in samples treated with NP0 and PLGA-PEIH (the higher charge NPs), which was not present in samples treated with NP5000 or PLGA-PEIL (the lower charge NPs).