Injectable, spontaneously assembling inorganic scaffolds modulate immune cells in vivo and increase vaccine efficacy

Materials implanted in the body to program host immune cells are a promising alternative to transplantation of ex vivo–manipulated cells to direct an immune response, but required a surgical procedure. Here we demonstrate that high-aspectratio, mesoporous silica rods (MSRs) injected with a needle spontaneously assemble in vivo to form macroporous structures that provide a 3D cellular microenvironment for host immune cells. In mice, substantial numbers of DCs are recruited to the pores between the scaffold rods. The recruitment of DCs and their subsequent homing to lymph nodes can be modulated by sustained release of inflammatory signals and adjuvants from the scaffold. Moreover, injection of an MSR-based vaccine formulation enhances systemic TH1 and TH2 serum antibody and cytotoxic T cell levels compared to bolus controls. These findings suggest that injectable MSRs may serve as a multifunctional vaccine platform to modulate host immune cell function and provoke adaptive immune responses

Effect of Pore Structure of Macroporous Poly(Lactide-<i>co</i>-Glycolide) Scaffolds on the <i>in Vivo</i> Enrichment of Dendritic Cells

The <i>in vivo</i> enrichment of dendritic cells (DCs) in implanted macroporous scaffolds is an emerging strategy to modulate the adaptive immune system. The pore architecture is potentially one of the key factors in controlling enrichment of DCs. However, there have been few studies examining the effects of scaffold pore structure on <i>in vivo</i> DC enrichment. Here we present the effects of surface porosity, pore size, and pore volume of macroporous poly­(lactide-<i>co</i>-glycolide) (PLG) scaffolds encapsulating granulocyte macrophage colony-stimulating factor (GM-CSF), an inflammatory chemoattractant, on the <i>in vivo</i> enrichment of DCs. Although <i>in vitro</i> cell seeding studies using PLG scaffolds without GM-CSF showed higher cell infiltration in scaffolds with higher surface porosity, <i>in vivo</i> results revealed higher DC enrichment in GM-CSF loaded PLG scaffolds with lower surface porosity despite a similar level of GM-CSF released. The diminished compressive modulus of high surface porosity scaffolds compared to low surface porosity scaffolds lead to the significant shrinkage of these scaffolds <i>in vivo,</i> suggesting that the mechanical strength of scaffolds was critical to maintain a porous structure <i>in vivo</i> for accumulating DCs. The pore volume was also found to be important in total number of recruited cells and DCs <i>in vivo.</i> Varying the pore size significantly impacted the total number of cells, but similar numbers of DCs were found as long as the pore size was above 10–32 μm. Collectively, these results suggested that one can modulate <i>in vivo</i> enrichment of DCs by altering the pore architecture and mechanical properties of PLG scaffolds

Oligolysine-based coating protects DNA nanostructures from low-salt denaturation and nuclease degradation

DNA nanostructures have evoked great interest as potential therapeutics and diagnostics due to ease and robustness of programming their shapes, site-specific functionalizations and responsive behaviours. However, their utility in biological fluids can be compromised through denaturation induced by physiological salt concentrations and degradation mediated by nucleases. Here we demonstrate that DNA nanostructures coated by oligolysines to 0.5:1 N:P (ratio of nitrogen in lysine to phosphorus in DNA), are stable in low salt and up to tenfold more resistant to DNase I digestion than when uncoated. Higher N:P ratios can lead to aggregation, but this can be circumvented by coating instead with an oligolysine-PEG copolymer, enabling up to a 1,000-fold protection against digestion by serum nucleases. Oligolysine-PEG-stabilized DNA nanostructures survive uptake into endosomal compartments and, in a mouse model, exhibit a modest increase in pharmacokinetic bioavailability. Thus, oligolysine-PEG is a one-step, structure-independent approach that provides low-cost and effective protection of DNA nanostructures for in vivo applications