Previous ELISPOT assays exposed AuNVs directly to splenocytes, which was a rudimentary way to evaluate the effects of AuNVs. Although there are some antigen-presenting cells in the splenocyte

mixture, the result would be occasionally inconclusive. Thus, to mimic physiological conditions, the AuNVs were incubated MK-1775 research buy with dendritic cells prior to exposure to the splenocytes, eliminating any AuNV direct influence on the splenocytes. The BMDCs were cultured with AuNVs for 24 h. Then, they were washed to remove excess AuNVs and were used as stimulator cells for SN-38 antigen-specific splenocytes on IFN-γ ELISPOT plates. The DC-to-splenocyte ELISPOT assay can then be used to determine whether the peptides conjugated onto AuNPs can be free for MHC loading. Using this model, we evaluated two important factors for improved peptide conjugation onto AuNVs: conjugation duration and scheme. The optimization of conjugation duration is critical for sufficient peptide polymerization while minimizing unwanted cross-linking between the peptide side chains. For conjugation efficiency, we compared the efficacy of

AuNVs with varying durations from 30 min to 24 h. Figure  5A shows that AuNVs with 1-h conjugation duration provided the highest IFN-γ secretion (52 SFC). The AuNVs cross-linked for 2 h (24 SFC) were significantly lower than the 1-h particles, while the 30-min AuNVs (47 SFC) were not significantly different from the 1-h AuNVs. Figure 5 TPX-0005 solubility dmso Pregnenolone gp100 AuNVs ELISPOT results for conjugation time optimization and comparison of the two-step

and one-step methods. (A) The DC-to-pmel-1 splenocyte ELISPOT results for the gp100 AuNVs at different conjugation times. The 1-h method AuNVs gave the most optimal stimulation results between the various incubation times (single asterisk denotes p < 0.05). (B) The DC-to-pmel-1 splenocyte ELISPOT results for a comparison of the two-step and one-step method AuNV (double asterisk denotes p < 0.01). To compare the hydrodynamic particle size of the particles, the DLS data showed that the 1-h conjugation time formed the largest peptide-conjugated AuNVs (approximately 70 nm), which were still much smaller than most liposomal and polymeric formulations (Additional file 1: Figure S4) [8, 9]. This advantage can potentially improve lymphatic drainage of the AuNVs. The 2-h AuNVs showed a smaller particle size that supports the hypothesis that synthesis time can cause excessive cross-linkage from the side groups on the peptides and fold on top of the particle. The scheme used for EDC/sulfo-NHS conjugation is another important factor. As previously mentioned, the conventional two-step conjugation method was designed to minimize affecting the second protein’s carboxyls. However, in our situation, enhanced activation of peptide carboxyl groups will be useful for allowing the peptides to link together.