Silica nanoparticles as substrates for chelator-free labeling of oxophilic radioisotopes.

Chelator-free nanoparticles for intrinsic radiolabeling are highly desirable for whole-body imaging and therapeutic applications. Several reports have successfully demonstrated the principle of intrinsic radiolabeling. However, the work done to date has suffered from much of the same specificity issues as conventional molecular chelators, insofar as there is no singular nanoparticle substrate that has proven effective in binding a wide library of radiosotopes. Here we present amorphous silica nanoparticles as general substrates for chelator-free radiolabeling and demonstrate their ability to bind six medically relevant isotopes of various oxidation states with high radiochemical yield. We provide strong evidence that the stability of the binding correlates with the hardness of the radioisotope, corroborating the proposed operating principle. Intrinsically labeled silica nanoparticles prepared by this approach demonstrate excellent in vivo stability and efficacy in lymph node imaging.

Genetic program activity delineates risk, relapse, and therapy responsiveness in multiple myeloma.

Despite recent advancements in the treatment of multiple myeloma (MM), nearly all patients ultimately relapse and many become refractory to multiple lines of therapies. Therefore, we not only need the ability to predict which patients are at high risk for disease progression but also a means to understand the mechanisms underlying their risk. Here, we report a transcriptional regulatory network (TRN) for MM inferred from cross-sectional multi-omics data from 881 patients that predicts how 124 chromosomal abnormalities and somatic mutations causally perturb 392 transcription regulators of 8549 genes to manifest in distinct clinical phenotypes and outcomes. We identified 141 genetic programs whose activity profiles stratify patients into 25 distinct transcriptional states and proved to be more predictive of outcomes than did mutations. The coherence of these programs and accuracy of our network-based risk prediction was validated in two independent datasets. We observed subtype-specific vulnerabilities to interventions with existing drugs and revealed plausible mechanisms for relapse, including the establishment of an immunosuppressive microenvironment. Investigation of the t(4;14) clinical subtype using the TRN revealed that 16% of these patients exhibit an extreme-risk combination of genetic programs (median progression-free survival of 5 months) that create a distinct phenotype with targetable genes and pathways.

High-speed Raman-encoded molecular imaging of freshly excised tissue surfaces with topically applied SERRS nanoparticles.

Surface-enhanced Raman scattering (SERS) nanoparticles (NPs) are increasingly being engineered for a variety of disease-detection and treatment applications. For example, we have previously developed a fiber-optic Raman-encoded molecular imaging (REMI) system for spectral imaging of biomarker-targeted SERS NPs topically applied on tissue surfaces to identify residual tumors at surgical margins. Although accurate tumor detection was achieved, the commercial SERS NPs used in our previous studies lacked the signal strength to enable high-speed imaging with high pixel counts (large fields of view and/or high spatial resolution), which limits their use for certain time-constrained clinical applications. As a solution, we explored the use of surface-enhanced resonant Raman scattering (SERRS) NPs to enhance imaging speeds. The SERRS NPs were synthesized de novo, and then conjugated to HER2 antibodies to achieve high binding affinity, as validated by flow cytometry. Under identical tissue-staining and imaging conditions, the targeted SERRS NPs enabled reliable identification of HER2-overexpressed tumor xenografts with 50-fold-enhanced imaging speed compared with our standard targeted SERS NPs. This enables our REMI system to image tissue surfaces at a rate of 150 cm2 per minute at a spatial resolution of 0.5 mm.

Folate-Targeted Surface-Enhanced Resonance Raman Scattering Nanoprobe Ratiometry for Detection of Microscopic Ovarian Cancer.

Ovarian cancer has a unique pattern of metastatic spread, in that it initially spreads locally within the peritoneal cavity. This is in contrast to most other cancer types, which metastasize early on via the bloodstream to distant sites. This unique behavior opens up an opportunity for local application of both therapeutic and imaging agents. Upon initial diagnosis, 75% of patients already present with diffuse peritoneal spread involving abdominal organs. Complete resection of all tumor implants has been shown to be a major factor for improved survival. Unfortunately, it is currently not possible for surgeons to visualize microscopic implants, impeding their removal and leading to tumor recurrences and poor outcomes in most patients. Thus, there is a great need for new intraoperative imaging techniques that can overcome this hurdle. We devised a method that employs folate receptor (FR)-targeted surface-enhanced resonance Raman scattering (SERRS) nanoparticles (NPs), as folate receptors are typically overexpressed in ovarian cancer. We report a robust ratiometric imaging approach using anti-FR-SERRS-NPs (αFR-NPs) and nontargeted SERRS-NPs (nt-NPs) multiplexing. We term this method "topically applied surface-enhanced resonance Raman ratiometric spectroscopy" (TAS3RS ("tasers") for short). TAS3RS successfully enabled the detection of tumor lesions in a murine model of human ovarian adenocarcinoma regardless of their size or localization. Tumors as small as 370 µm were detected, as confirmed by bioluminescence imaging and histological staining. TAS3RS holds promise for intraoperative detection of microscopic residual tumors and could reduce recurrence rates in ovarian cancer and other diseases with peritoneal spread.

Cancer imaging using surface-enhanced resonance Raman scattering nanoparticles.

The unique spectral signatures and biologically inert compositions of surface-enhanced resonance Raman scattering (SERRS) nanoparticles make them promising contrast agents for in vivo cancer imaging. Our SERRS nanoparticles consist of a 60-nm gold nanoparticle core that is encapsulated in a 15-nm-thick silica shell wherein the resonant Raman reporter is embedded. Subtle aspects of their preparation can shift their limit of detection by orders of magnitude. In this protocol, we present the optimized, step-by-step procedure for generating reproducible SERRS nanoparticles with femtomolar (10-15 M) limits of detection. We provide ways of characterizing the optical properties of SERRS nanoparticles using UV/VIS and Raman spectroscopy, and their physicochemical properties using transmission electron microscopy and nanoparticle tracking analysis. We introduce several applications of these nanoprobes for biomedical research, with a focus on intraoperative cancer imaging via Raman imaging. A detailed account is provided for successful i.v. administration of SERRS nanoparticles such that delineation of cancerous lesions can be achieved in vivo and ex vivo on resected tissues without the need for specific biomarker targeting. This straightforward, yet comprehensive, protocol-from initial de novo gold nanoparticle synthesis to SERRS nanoparticle contrast-enhanced preclinical Raman imaging in animal models-takes ∼96 h.

Chelator-Free Radiolabeling of SERRS Nanoparticles for Whole-Body PET and Intraoperative Raman Imaging.

A single contrast agent that offers whole-body non-invasive imaging along with the superior sensitivity and spatial resolution of surface-enhanced resonance Raman scattering (SERRS) imaging would allow both pre-operative mapping and intraoperative imaging and thus be highly desirable. We hypothesized that labeling our recently reported ultrabright SERRS nanoparticles with a suitable radiotracer would enable pre-operative identification of regions of interest with whole body imaging that can be rapidly corroborated with a Raman imaging device or handheld Raman scanner in order to provide high precision guidance during surgical procedures. Here we present a straightforward new method that produces radiolabeled SERRS nanoparticles for combined positron emission tomography (PET)-SERRS tumor imaging without requiring the attachment of molecular chelators. We demonstrate the utility of these PET-SERRS nanoparticles in several proof-of-concept studies including lymph node (LN) tracking, intraoperative guidance for LN resection, and cancer imaging after intravenous injection. We anticipate that the radiolabeling method presented herein can be applied generally to nanoparticle substrates of various materials by first coating them with a silica shell and then applying the chelator-free protocol.

Raman-Encoded Molecular Imaging with Topically Applied SERS Nanoparticles for Intraoperative Guidance of Lumpectomy.

Intraoperative identification of carcinoma at lumpectomy margins would enable reduced re-excision rates, which are currently as high as 20% to 50%. Although imaging of disease-associated biomarkers can identify malignancies with high specificity, multiplexed imaging of such biomarkers is necessary to detect molecularly heterogeneous carcinomas with high sensitivity. We have developed a Raman-encoded molecular imaging (REMI) technique in which targeted nanoparticles are topically applied on excised tissues to enable rapid visualization of a multiplexed panel of cell surface biomarkers at surgical margin surfaces. A first-ever clinical study was performed in which 57 fresh specimens were imaged with REMI to simultaneously quantify the expression of four biomarkers HER2, ER, EGFR, and CD44. Combined detection of these biomarkers enabled REMI to achieve 89.3% sensitivity and 92.1% specificity for the detection of breast carcinoma. These results highlight the sensitivity and specificity of REMI to detect biomarkers in freshly resected tissue, which has the potential to reduce the rate of re-excision procedures in cancer patients. Cancer Res; 77(16); 4506-16. ©2017 AACR.

Surfactant-Free Shape Control of Gold Nanoparticles Enabled by Unified Theoretical Framework of Nanocrystal Synthesis.

Gold nanoparticles have unique properties that are highly dependent on their shape and size. Synthetic methods that enable precise control over nanoparticle morphology currently require shape-directing agents such as surfactants or polymers that force growth in a particular direction by adsorbing to specific crystal facets. These auxiliary reagents passivate the nanoparticles' surface, and thus decrease their performance in applications like catalysis and surface-enhanced Raman scattering. Here, a surfactant- and polymer-free approach to achieving high-performance gold nanoparticles is reported. A theoretical framework to elucidate the growth mechanism of nanoparticles in surfactant-free media is developed and it is applied to identify strategies for shape-controlled syntheses. Using the results of the analyses, a simple, green-chemistry synthesis of the four most commonly used morphologies: nanostars, nanospheres, nanorods, and nanoplates is designed. The nanoparticles synthesized by this method outperform analogous particles with surfactant and polymer coatings in both catalysis and surface-enhanced Raman scattering.

Detection of Lymph Node Metastases with SERRS Nanoparticles.

PURPOSE: The accurate detection of lymph node metastases in prostate cancer patients is important to direct treatment decisions. Our goal was to develop an intraoperative imaging approach to distinguish normal from metastasized lymph nodes. We aimed at developing and testing gold-silica surface-enhanced resonance Raman spectroscopy (SERRS) nanoparticles that demonstrate high uptake within normal lymphatic tissue and negligible uptake in areas of metastatic replacement. PROCEDURES: We evaluated the ability of SERRS nanoparticles to delineate lymph node metastases in an orthotopic prostate cancer mouse model using PC-3 cells transduced with mCherry fluorescent protein. Tumor-bearing mice (n = 6) and non-tumor-bearing control animals (n = 4) were injected intravenously with 30 fmol/g SERRS nanoparticles. After 16-18 h, the retroperitoneal lymph nodes were scanned in situ and ex vivo with a Raman imaging system and a handheld Raman scanner and data corroborated with fluorescence imaging for mCherry protein expression and histology. RESULTS: The SERRS nanoparticles demonstrated avid homing to normal lymph nodes, but not to metastasized lymph nodes. In cases where lymph nodes were partially infiltrated by tumor cells, the SERRS signal correctly identified, with sub-millimeter precision, healthy from metastasized components. CONCLUSIONS: This study serves as a first proof-of-principle that SERRS nanoparticles enable high precision and rapid intraoperative discrimination between normal and metastasized lymph nodes.

Rational design of a chalcogenopyrylium-based surface-enhanced resonance Raman scattering nanoprobe with attomolar sensitivity.

High sensitivity and specificity are two desirable features in biomedical imaging. Raman imaging has surfaced as a promising optical modality that offers both. Here we report the design and synthesis of a group of near-infrared absorbing 2-thienyl-substituted chalcogenopyrylium dyes tailored to have high affinity for gold. When adsorbed onto gold nanoparticles, these dyes produce biocompatible SERRS nanoprobes with attomolar limits of detection amenable to ultrasensitive in vivo multiplexed tumour and disease marker detection.

Surface-enhanced resonance Raman scattering nanostars for high-precision cancer imaging.

The inability to visualize the true extent of cancers represents a significant challenge in many areas of oncology. The margins of most cancer types are not well demarcated because the cancer diffusely infiltrates the surrounding tissues. Furthermore, cancers may be multifocal and characterized by the presence of microscopic satellite lesions. Such microscopic foci represent a major reason for persistence of cancer, local recurrences, and metastatic spread, and are usually impossible to visualize with currently available imaging technologies. An imaging method to reveal the true extent of tumors is desired clinically and surgically. We show the precise visualization of tumor margins, microscopic tumor invasion, and multifocal locoregional tumor spread using a new generation of surface-enhanced resonance Raman scattering (SERRS) nanoparticles, which are termed SERRS nanostars. The SERRS nanostars feature a star-shaped gold core, a Raman reporter resonant in the near-infrared spectrum, and a primer-free silication method. In genetically engineered mouse models of pancreatic cancer, breast cancer, prostate cancer, and sarcoma, and in one human sarcoma xenograft model, SERRS nanostars enabled accurate detection of macroscopic malignant lesions, as well as microscopic disease, without the need for a targeting moiety. Moreover, the sensitivity (1.5 fM limit of detection) of SERRS nanostars allowed imaging of premalignant lesions of pancreatic and prostatic neoplasias. High sensitivity and broad applicability, in conjunction with their inert gold-silica composition, render SERRS nanostars a promising imaging agent for more precise cancer imaging and resection.