Understanding cell biology greatly benefits from the development of advanced diagnostic probes. Here we introduce a 22-nm spaser (plasmonic nanolaser) with the ability to serve as a super-bright, water-soluble, biocompatible probe capable of generating stimulated emission directly inside living cells and animal tissues. We have demonstrated a lasing regime associated with the formation of a dynamic vapour nanobubble around the spaser that leads to giant spasing with emission intensity and spectral width >100 times brighter and 30-fold narrower, respectively, than for quantum dots. The absorption losses in the spaser enhance its multifunctionality, allowing for nanobubble-amplified photothermal and photoacoustic imaging and therapy. Furthermore, the silica spaser surface has been covalently functionalized with folic acid for molecular targeting of cancer cells. All these properties make a nanobubble spaser a promising multimodal, super-contrast, ultrafast cellular probe with a single-pulse nanosecond excitation for a variety ofin vitroandin vivobiomedical applications.

Noninvasive label-free photoacoustic detection of circulating tumor cells was demonstrated directly in the bloodstream of patients with melanoma.

Circulating cells, bacteria, proteins, microparticles, and DNA in cerebrospinal fluid (CSF) are excellent biomarkers of many diseases, including cancer and infections. However, the sensitivity of existing methods is limited in their ability to detect rare CSF biomarkers at the treatable, early-stage of diseases. Here, we introduce novel CSF tests based on in vivo photoacoustic flow cytometry (PAFC) and ex vivo photothermal scanning cytometry. In the CSF of tumor-bearing mice, we molecularly detected in vivo circulating tumor cells (CTCs) before the development of breast cancer brain metastasis with 20-times higher sensitivity than with current assays. For the first time, we demonstrated assessing three pathways (i.e., blood, lymphatic, and CSF) of CTC dissemination, tracking nanoparticles in CSF in vivo and their imaging ex vivo. In label-free CSF samples, we counted leukocytes, erythrocytes, melanoma cells, and bacteria and imaged intracellular cytochromes, hemoglobin, melanin, and carotenoids, respectively. Taking into account the safety of PAFC, its translation for use in humans is expected to improve disease diagnosis beyond conventional detection limits. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Bacterial infections are a primary cause of morbidity and mortality worldwide. Bacteremia is a particular concern owing to the possibility of septic shock and the development of metastatic infections. Treatment of bacteremia is increasingly compromised by the emergence of antibiotic resistant strains, creating an urgent need for alternative therapy. Here, we introduce a method for in vivo photoacoustic (PA) detection and photothermal (PT) eradication of Staphylococcus aureus in tissue and blood. We show that this method could be applicable for label-free diagnosis and treatment of in the bloodstream using intrinsic near-infrared absorption of endogenous carotenoids with nonlinear PA and PT contrast enhancement. To improve sensitivity and specificity for detection of circulating bacteria cells (CBCs), two-color gold and multilayer magnetic nanoparticles with giant amplifications of PA and PT contrasts were functionalized with an antibody cocktail for molecular targeting of S. aureus surface-associated markers such as protein A and lipoprotein. With a murine model, the utility of this approach was demonstrated for ultrasensitive detection of CBCs with threshold sensitivity as low as 0.5 CBCs/mL, in vivo magnetic enrichment of CBCs, PT eradication of CBCs, and real-time monitoring of therapeutic efficacy by CBC counting. Our PA-PT nano-theranostic platform, which integrates in vivo multiplex targeting, magnetic enrichment, signal amplification, multicolor recognition, and feedback control, could be used as a biological tool to gain insights on dissemination pathways of CBCs, infection progression by bacteria re-seeding, and sepsis development and treatment, and could potentially be feasible in humans, especially using bypass schematic.

In vivo photoacoustic (PA) flow cytometry (PAFC) has already demonstrated a great potential for the diagnosis of deadly diseases through ultrasensitive detection of rare disease‐associated circulating markers in whole blood volume. Here, we demonstrate the first application of this powerful technique for early diagnosis of malaria through label‐free detection of malaria parasite‐produced hemozoin in infected red blood cells (iRBCs) as high‐contrast PA agent. The existing malaria tests using blood smears can detect the disease at 0.001–0.1% of parasitemia. On the contrary, linear PAFC showed a potential for noninvasive malaria diagnosis at an extremely low level of parasitemia of 0.0000001%, which is ∼10³ times better than the existing tests. Multicolor time‐of‐flight PAFC with high‐pulse repetition rate lasers at wavelengths of 532, 671, and 820 nm demonstrated rapid spectral and spatial identification and quantitative enumeration of individual iRBCs. Integration of PAFC with fluorescence flow cytometry (FFC) provided real‐time simultaneous detection of single iRBCs and parasites expressing green fluorescence proteins, respectively. A combination of linear and nonlinear nanobubble‐based multicolor PAFC showed capability to real‐time control therapy efficiency by counting of iRBCs before, during, and after treatment. Our results suggest that high‐sensitivity, high‐resolution ultrafast PAFC–FFC platform represents a powerful research tool to provide the insight on malaria progression through dynamic study of parasite–cell interactions directly in bloodstream, whereas portable hand‐worn PAFC device could be broadly used in humans for early malaria diagnosis. © 2016 International Society for Advancement of Cytometry