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Methods to noninvasively increase and assess T cell infiltration are critical for success of adoptive cell therapy (ACT) of solid tumors where only a small fraction of adoptive T cells typically accumulates at the target. We developed an approach based on photoacoustic (PA) and ultrasound (US) imaging to visualize magnetic field driven accumulation of T cells tagged with photo-magnetic nanoparticles (PMNPs). Specifically, Au@Fe3O4 shell-core PMNPs (200 nm diameter), absorbing at 1064 nm wavelength, were synthesized and characterized using a UV-Vis-NIR spectrophotometry, dynamic light scattering (DLS), and transmission electron microscopy (TEM). Ovalbumin (OVA)-targeted PMNP-tagged OT1 murine primary T cells were injected intravenously into OVA-expressing tumor-bearing C57BL/6 mice. US/PA imaging (20 MHz, 1064 nm and 680–970 nm, Vevo LAZR, Visualsonics Inc.) of the primary tumor and regional lymph nodes showed accumulation of PMNP-tagged T cells. Our results indicate feasibility of the T cell tagging with PMNPs and magnetic delivery of adoptive PMNP-tagged T cells using US/PA imaging thus providing critical imaging feedback to improve the adoptive T cell therapy of solid tumors. Overall, our studies show that a synergistic combination of US/PA imaging and magnetic delivery of nanoparticle (NP)-tagged adoptive T cells can expedite development, translation, and expansion of ACT.

We recently reported a real-time method to measure heparin in human whole blood based on the photoacoustic change of methylene blue (MB). Intriguingly, the MB behaved unlike other "turn on" photoacoustic probes-the absorbance decreased as the photoacoustic signal increased. The underlying mechanism was not clear and motivated this study. We studied the binding mechanism of MB and heparin in water and phosphate buffer saline (PBS) with both experimental and computational methods. We found that the photoacoustic enhancement of the MB-heparin mixture was a result of MB-heparin aggregation due to charge neutralization and resulting sequestration of MB in these aggregates. The sequestration of MB in the MB-heparin aggregates led to decreased absorbance-there was simply less free dye in solution to absorb light. The highest photoacoustic signal and aggregation occurred when the number of negatively charged sulfate groups on heparin was approximately equal to the number of positively charged MB molecule. The MB-heparin aggregates dissociated when there were more sulfated groups from heparin than MB molecules because of the electrostatic repulsion between negatively charged sulfate groups. PBS facilitated MB dimer formation regardless of heparin concentration and reprecipitated free MB in aggregates due to ionic strength and ionic shielding. Further molecular dynamics experiments found that binding of heparin occurred at the sulfates and glucosamines in heparin. Phosphate ions could interact with the heparin via sodium ions to impair the MB-heparin binding. Finally, our model found 3.7-fold more MB dimerization upon addition of heparin in MB solution confirming that heparin facilitates MB aggregation. We conclude that the addition of heparin in MB decreases the absorbance of the sample because of MB-heparin aggregation leading to fewer MB molecules in solution; however, the aggregation also increases the PA intensity because the MB molecules in the MB-heparin aggregate have reduced degrees of freedom and poor heat transfer to solvent.

Transvaginal ultrasound is widely used for ovarian cancer screening but has a high false positive rate. Photoacoustic imaging provides additional optical contrast to supplement ultrasound and might be able to improve the accuracy of screening. Here, we report two copper sulfide (CuS) nanoparticles types (nanodisks and triangular nanoprisms) as the photoacoustic contrast agents for imaging ovarian cancer. Both CuS nanoprisms and nanodisks were ~6 nm thick and ~26 nm wide and were coated with poly(ethylene glycol) to make them colloidally stable in phosphate buffered saline (PBS) for at least 2 weeks. The CuS nanodisks and nanoprisms revealed strong localized surface plasmon resonances with peak maxima at 1145 nm and 1098 nm, respectively. Both nanoparticles types had strong and stable photoacoustic intensity with detection limits below 120 pM. The circular CuS nanodisk remained in the circulation of nude mice (n=4) and xenograft 2008 ovarian tumors (n=4) 17.9-fold and 1.8-fold more than the triangular nanoprisms, respectively. Finally, the photoacoustic intensity of the tumors from the mice (n=3) treated with CuS nanodisks was 3.0-fold higher than the baseline. The tumors treated with nanodisks had a characteristic peak at 920 nm in the spectrum to potentially differentiate the tumor from adjacent tissues.

The interaction between methylene blue (MB) and sodium dodecyl sulfate (SDS) has been widely studied spectroscopically, but details about their interactions remain unclear. Here, we combined photoacoustic (PA) imaging with nanoparticle tracking analysis (NTA) and spectroscopy to further elucidate this interaction. PA imaging of 0.05 mM MB showed a 492-fold increase in intensity upon the addition of 3.47 mM SDS. Higher concentrations above SDS’s critical micelle concentration (CMC) at 8.67 mM decreased the PA intensity by 54 times. Relative quantum yield measurements indicated that PA intensity increased as a result of fluorescence quenching. Meanwhile, NTA indicated an increased number of nonmicellar MB/SDS clusters at SDS concentrations below the CMC varying in size from 80 to 400 nm as well as a decreased number above the CMC. This trend suggested that MB/SDS clusters are responsible for the PA intensity enhancement. Comparison of PA intensities and spectral shifts with MB/hexadecyltrimethylammonium bromide, MB/sodium octyl sulfate, and MB/sodium chloride demonstrated that MB was bound to the sulfate moiety of SDS before and after micellization. Our observations suggest that MB forms aggregates with SDS at premicellar concentrations, and the MB aggregates disassociate as monomers that are bound to the sulfate moiety of SDS at micellar concentrations. These findings further clarify the process by which MB and SDS interact and demonstrate the potential for developing MB-/SDS-based contrast agents.

Ultrasound is critical in many areas of medicine including obstetrics, oncology, and cardiology with emerging applications in regenerative medicine. However, one critical limitation of ultrasound is the low contrast of target tissue over background. Here, we describe a novel cup-shaped silica nanoparticle that is reminiscent of exosomes and that has significant ultrasound impedance mismatch for labelling stem cells for regenerative medicine imaging. These exosome-like silica nanoparticles (ELS) were created through emulsion templating and the silica precursors bis(triethoxysilyl)ethane (BTSE) and bis(3-trimethoxysilyl-propyl)amine (TSPA). We found that 40% TSPA resulted in the exosome like-morphology and a positive charge suitable for labelling mesenchymal stem cells. We then compared this novel structure to other silica structures used in ultrasound including Stober silica nanoparticles (SSN), MCM-41 mesoporous silica nanoparticles (MSN), and mesocellular foam silica nanoparticles (MCF) and found that the ELS offered enhanced stem cell signal due to its positive charge to facilitate cell uptake as well as inherently increased echogenicity. The in vivo detection limits were

The personal ultraviolet (UV) dosimeter is a useful measurement tool to prevent UV induced dermal damages; however, conventional digital dosimeters are either bulky or require external power sources. Here, a wearable, colorimetric UV film dosimeter that provides color transition, from purple to transparent, is reported to indicate the UV dose. The film dosimeter is made of a purple photodegradable dye ((2Z,6Z)-2,6-bis(2-(2,6-diphenyl-4H-thiopyran-4-ylidene)ethylidene)cyclohexanone or DTEC) blended in low density polyethylene film. The DTEC film discolored 3.3 times more under the exposure of UV light (302 nm) than visible light (543 nm), and a UV bandpass filter is developed to increase this selectivity to UV light. The DTEC film completely discolors to transparency in 2 h under an AM 1.5 solar simulator, suggesting the potential as an indicator for individuals with types I-VI skin to predict interventions to avoid sunburn. Finally, the DTEC film is integrated with the UV bandpass filter on a wristband to function as a wearable dosimeter for low cost and convenient monitoring of sunlight exposure.