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We studied the diffusion of gold nanoparticles within entangled solutions and gels formed by high molecular weight (M w = 89000 g/mol) poly­(vinyl alcohol) (PVA) in water by using fluctuation correlation spectroscopy (FCS). The nanoparticle size (2R) was varied between 5 and 30 nm, and the PVA volume fraction (ϕ) was chosen to be in the entangled regime. We found that existing hydrodynamic and obstruction models are inadequate to describe the size dependence of the particle diffusion coefficient (D). For size ratios x = 2R/a e ≈ 0.5–2.5, where a e is the entanglement tube diameter in the solution, our results suggest a functional form for D ∼ exp­(−κx), where κ ≈ 1.4. This result qualitatively agrees with the scaling theory prediction of hopping motion for particles within entangled polymer solutions. For larger particles at higher volume fractions, an additional sharp slowing down of the particle motion was observed, which also exhibited an exponential dependence on the size ratio, but with a much higher value of κ ≈ 7.5. Such a rare hopping process can be explained qualitatively by recently developed force-based nonlinear Langevin theory.

We studied the diffusion of charged gold nanoparticles within a semidilute solution of weakly charged polyelectrolyte, polyacrylic acid (PAA) of high molecular weight (Mw = 106 g mol−1) by using fluorescence correlation spectroscopy (FCS).

The paracrine and autocrine processes of the host response play an integral role in the success of scaffold-based tissue regeneration. Recently, the immunomodulatory scaffolds have received huge attention for modulating inflammation around the host tissue through releasing anti-inflammatory cytokine. However, controlling the inflammation and providing a sustained release of anti-inflammatory cytokine from the scaffold in the digestive inflammatory environment are predicated upon a comprehensive understanding of three fundamental questions. (1) How does the release rate of cytokine from the scaffold change in the digestive inflammatory environment? (2) Can we prevent the premature scaffold degradation and burst release of the loaded cytokine in the digestive inflammatory environment? (3) How does the scaffold degradation prevention technique affect the immunomodulatory capacity of the scaffold? This study investigated the impacts of the digestive inflammatory environment on scaffold degradation and how pre-mature degradation can be prevented using genipin crosslinking and how genipin crosslinking affects the interleukin-4 (IL-4) release from the scaffold and differentiation of naïve macrophages (M0). Our results demonstrated that the digestive inflammatory environment (DIE) attenuates protein retention within the scaffold. Over 14 days, the encapsulated protein released 46% more in DIE than in phosphate buffer saline (PBS), which was improved through genipin crosslinking. We have identified the 0.5 (w/v) genipin concentration as an optimal concentration for improved IL-4 released from the scaffold, cell viability, mechanical strength, and scaffold porosity, and immunomodulation studies. The IL-4 released from the injectable scaffold could differentiate naïve macrophages to an anti-inflammatory (M2) lineage; however, upon genipin crosslinking, the immunomodulatory capacity of the scaffold diminished significantly, and pro-inflammatory markers were expressed dominantly.