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Mass cytometry (MC) is an emerging and powerful bioanalytical technique for high-dimensional single-cell analysis. While metal-chelating polymers (MCPs) have been the most successful mass tag reagents for MC, nanoparticle (NP)-based mass tag reagents are of great interest to improve the sensitivity of MC toward low-abundance biomarkers. Here we present a new structure design for potential MC probes using multifunctionalized mesoporous silica nanoparticles (MSNs), modified with zwitterionic sulfobetaine silanes and long-chain polyethylene glycol silanes (PEG5k, M= 5000). The resulting methoxy-terminated NPs (PMSN-Zwi-mPEG5k) displayed uniform size, good redispersibility and colloidal stability, as well as versatility in accommodating 13 types of lanthanides. They exhibited the capacity to carry up to 7.4 × 104Tb ions per NP, with negligible ion loss observed in both H2O and 1× PBS buffer. We investigated the interactions of these functionalized NPs with serum proteins using UV–vis, and with peripheral blood mononuclear cells (PBMCs) using MC. By varying PEG5kchain density on NP surface, we could minimize their nonspecific binding (NSB) to human serum albumin proteins, while also reducing their NSB to PBMCs at the titer of 1000 NPs/cell. Additionally, unconjugated NPs showed good compatibility with commercial Maxpar MCP mass tags in a 10-plex assay for PBMCs staining. Under these optimized conditions, N3-terminated NPs (PMSN-Zwi-PEG5k-N3) were synthesized and conjugated with antibiotin antibodies (Abs), resulting in effective binding of biotin Cy5 molecules. We finally compared eight different bioconjugation conditions to maximize bioconjugation efficiency with retention of Ab function. These preliminary findings demonstrate the fundamental technical capabilities and promising prospects for the future application of MSN-based mass tag reagents in MC.

In this study, we investigated convection-enhanced delivery (CED) of 23 ± 3 nm gold nanoparticles (AuNPs) labeled with the β-particle-emitting radionuclide 177Lu (177Lu-AuNPs) for treatment of orthotopic U251-Luc human glioblastoma multiforme (GBM) tumors in NRG mice. The cytotoxicity in vitro of 177Lu-AuNPs (0.0–2.0 MBq, 4 × 1011AuNPs) on U251-Luc cells was also studied by a clonogenic survival assay, and DNA double-strand breaks (DSBs) caused by β-particle emissions of 177Lu were measured by confocal immunofluorescence microscopy for γH2AX. NRG mice with U251-Luc tumors in the right cerebral hemisphere of the brain were treated by CED of 1.1 ± 0.2 MBq of 177Lu-AuNPs (4 × 1011AuNPs). Control mice received unlabeled AuNPs or normal saline. Tumor retention of 177Lu-AuNPs was assessed by single-photon emission computed tomography/computed tomography (SPECT/CT) imaging and biodistribution studies. Radiation doses were estimated for the tumor, brain, and other organs. The effectiveness for treating GBM tumors was determined by bioluminescence imaging (BLI) and T2-weighted magnetic resonance imaging (MRI) and by Kaplan–Meier median survival. Normal tissue toxicity was assessed by monitoring body weight and hematology and blood biochemistry analyses at 14 d post-treatment. 177Lu-AuNPs (2.0 MBq, 4 × 1011AuNPs) decreased the clonogenic survival of U251-Luc cells to 0.005 ± 0.002 and increased DNA DSBs by 14.3-fold compared to cells treated with unlabeled AuNPs or normal saline. A high proportion of 177Lu-AuNPs was retained in the U251-Luc tumor in NRG mice up to 21 d with minimal re-distribution to the brain or other organs. The radiation dose in the tumor was high (599 Gy). The dose in the normal right cerebral hemisphere of the brain excluding the tumor was 93-fold lower (6.4 Gy), and 2000–3000-fold lower doses were calculated for the contralateral left cerebral hemisphere (0.3 Gy) or cerebellum (0.2 Gy). The doses in peripheral organs were <0.1 Gy. BLI revealed almost complete tumor growth arrest in mice treated with 177Lu-AuNPs, while tumors grew rapidly in control mice. MRI at 28 d post-treatment and histological staining showed no visible tumor in mice treated with 177Lu-AuNPs but large GBM tumors in control mice. All control mice reached a humane endpoint requiring sacrifice within 39 d (normal saline) or 45 d post-treatment (unlabeled AuNPs), while 5/8 mice treated with 177Lu-AuNPs survived up to 150 d. No normal tissue toxicity was observed in mice treated with 177Lu-AuNPs. We conclude that CED of 177Lu-AuNPs was highly effective for treating U251-Luc human GBM tumors in the brain in NRG mice at amounts that were non-toxic to normal tissues. These 177Lu-AuNPs administered by CED hold promise for treating patients with GBM to prevent recurrence and improve long-term outcome.