α-FeOOH-MoO3 Nanorod for Effective Photo-Fenton Degradation of Dyes and Antibiotics at a Wide Range of pH.

It's highly significant to develop a novel catalyst, which can be active at a wide range of pH, for an effective photo-Fenton reaction. In this work, α-FeOOH-MoO3 nanorod was prepared by a one-step hydrothermal method and applied in photo-Fenton degradation of organic pollutants. Benefit from the electron migration mechanism of Z-scheme and excellent photoelectric performance, the catalyst exhibited superior photo-Fenton activity in degradation of organic pollutants. In addition, the catalyst holds good stability after 5 recycles. These results demonstrated that this catalyst has wide application prospect in organic wastewater treatment.

Photoacoustic tomography imaging and estimation of oxygen saturation of hemoglobin in ocular tissue of rabbits.

This study evaluated in vivo imaging capabilities and safety of qualitative monitoring of oxygen saturation of hemoglobin (sO2) of rabbit ciliary body tissues obtained with acoustic resolution (AR) photoacoustic tomography (PAT). AR PAT was used to collect trans-scleral images from ciliary body vasculature of seven New Zealand White rabbits. The PAT sO2 measurements were obtained under the following conditions: when systemic sO2 as measured by pulse oximetry was between 100% and 99% (level 1); systemic sO2 as measured by pulse oximetry was between 98% and 90% (level 2); and systemic sO2 as measured by pulse oximetry was less than 90% (level 3). Following imaging, histological analysis of ocular tissue was conducted to evaluate for possible structural damage caused by the AR PAT imaging. AR PAT was able to resolve anatomical structures of the anterior segment of the eye, viewed through the cornea or anterior sclera. Histological studies revealed no ocular damage. On average, sO2 values (%) obtained with AR PAT were lower than sO2 values obtained with pulse oximetry (all p < 0.001): 86.28 ± 4.16 versus 99.25 ± 0.28, 84.09 ± 1.81 vs. 95.3 ± 2.6, and 64.49 ± 7.27 vs. 71.15 ± 10.21 for levels 1, 2 and 3 respectively. AR PAT imaging modality is capable of qualitative monitoring for deep tissue sO2 in rabbits. Further studies are needed to validate and modify the AR PAT modality specifically for use in human eyes. Having a safe, non-invasive method of in vivo imaging of sO2 in the anterior segment is important to studies evaluating the role of oxidative damage, hypoxia and ischemia in pathogenesis of ocular diseases.

Handheld photoacoustic microscopy to detect melanoma depth in vivo.

We developed handheld photoacoustic microscopy (PAM) to detect melanoma and determine tumor depth in nude mice in vivo. Compared to our previous PAM system for melanoma imaging, a new light delivery mechanism is introduced to improve light penetration. We show that melanomas with 4.1 and 3.7 mm thicknesses can be successfully detected in phantom and in in vivo experiments, respectively. With its deep melanoma imaging ability and handheld design, this system can be tested for clinical melanoma diagnosis, prognosis, and surgical planning for patients at the bedside.

Microcirculatory changes identified by photoacoustic microscopy in patients with complex regional pain syndrome type I after stellate ganglion blocks.

Complex regional pain syndrome (CRPS) is a chronic pain syndrome that causes intractable pain, disability, and poor quality of life for patients. The etiology and pathophysiology of CRPS are still poorly understood. Due to a lack of proper diagnostic tools, the prognosis of CRPS is primarily based on clinical observation. The objective of this work is to evaluate a new imaging modality, photoacoustic microscopy (PAM), for assisting diagnoses and monitoring the progress and treatment outcome of CRPS. Blood vasculature and oxygen saturation (sO2) were imaged by PAM from eight adult patients with CRPS-1. Patients' hands and cuticles were imaged both before and after stellate ganglion block (SGB) for comparison. For all patients, both vascular structure and sO2 could be assessed by PAM. In addition, more vessels and stronger signals were observed after SGB. The results show that PAM can help diagnose and monitor CRPS.

Radioactive 198Au-doped nanostructures with different shapes for in vivo analyses of their biodistribution, tumor uptake, and intratumoral distribution.

With Au nanocages as an example, we recently demonstrated that radioactive (198)Au could be incorporated into the crystal lattice of Au nanostructures for simple and reliable quantification of their in vivo biodistribution by measuring the γ radiation from (198)Au decay and for optical imaging by detecting the Cerenkov radiation. Here we extend the capability of this strategy to synthesize radioactive (198)Au nanostructures with a similar size but different shapes and then compare their biodistribution, tumor uptake, and intratumoral distribution using a murine EMT6 breast cancer model. Specifically, we investigated Au nanospheres, nanodisks, nanorods, and cubic nanocages. After PEGylation, an aqueous suspension of the radioactive Au nanostructures was injected into a tumor-bearing mouse intravenously, and their biodistribution was measured from the γ radiation while their tumor uptake was directly imaged using the Cerenkov radiation. Significantly higher tumor uptake was observed for the Au nanospheres and nanodisks relative to the Au nanorods and nanocages at 24 h postinjection. Furthermore, autoradiographic imaging was performed on thin slices of the tumor after excision to resolve the intratumoral distributions of the nanostructures. While both the Au nanospheres and nanodisks were only observed on the surfaces of the tumors, the Au nanorods and nanocages were distributed throughout the tumors.

Non-invasive and in situ characterization of the degradation of biomaterial scaffolds by volumetric photoacoustic microscopy.

Degradation is among the most important properties of biomaterial scaffolds, which are indispensable for regenerative medicine. The currently used method relies on the measurement of mass loss across different samples and cannot track the degradation of an individual scaffold in situ. Here we report, for the first time, the use of multiscale photoacoustic microscopy to non-invasively monitor the degradation of an individual scaffold. We could observe alterations to the morphology and structure of a scaffold at high spatial resolution and deep penetration, and more significantly, quantify the degradation of an individual scaffold as a function of time, both in vitro and in vivo. In addition, the remodeling of vasculature inside a scaffold can be visualized simultaneously using a dual-wavelength scanning mode in a label-free manner. This optoacoustic method can be used to monitor the degradation of individual scaffolds, offering a new approach to non-invasively analyze and quantify biomaterial-tissue interactions in conjunction with the assessment of in vivo vascular parameters.

Ultrasound-heated photoacoustic flowmetry.

We report the development of photoacoustic flowmetry assisted by high-intensity focused ultrasound (HIFU). This novel method employs HIFU to generate a heating impulse in the flow medium, followed by photoacoustic monitoring of the thermal decay process. Photoacoustic flowmetry in a continuous medium remains a challenge in the optical diffusive regime. Here, both the HIFU heating and photoacoustic detection can focus at depths beyond the optical diffusion limit (~1 mm in soft tissue). This method can be applied to a continuous medium, i.e., a medium without discrete scatterers or absorbers resolvable by photoacoustic imaging. Flow speeds up to 41 mm·s-1 have been experimentally measured in a blood phantom covered by 1.5-mm-thick tissue.

A Green Synthesis of Carbon Nanoparticle from Honey for Real-Time Photoacoustic Imaging.

Imaging sentinel lymph nodes (SLN) could provide us with critical information about the progression of a cancerous disease. Real-time high-resolution intraoperative photoacoustic imaging (PAI) in conjunction with a near infrared (NIR) probe may offer the opportunities for the immediate imaging for direct identification and resection of SLN or collecting tissue samples. In this work a commercially amenable synthetic methodology is revealed for developing luminescent carbon nanoparticles with rapid clearance properties. A one-pot "green" technique is pursued, which involved rapid surface passivation of carbon nanoparticles with organic macromolecules (e.g. polysorbate, polyethyleneglycol) in a solvent free condition. Interestingly, the naked carbon nanoparticles are derived for the first time, from commercial food grade honey. Surface coated particles are markedly smaller (~7 nm) than the previously explored particles (gold, SWNT, copper) for SLN imaging. Results indicate an exceptionally rapid signal enhancement (~2 min) of the SLN. Owing to their strong optical absorption in the near infrared region, tiny size and rapid lymphatic transport, this platform offers great potential for faster resection of SLN and may lower complications caused by axillary investigation for mismarking with dyes or low-resolution imaging techniques.

Integrated optical- and acoustic-resolution photoacoustic microscopy based on an optical fiber bundle.

Photoacoustic microscopy (PAM), whose spatial resolution and maximum imaging depth are both scalable, has made great progress in recent years. However, each PAM system currently achieves only one resolution with an associated maximum imaging depth. Here, we present an integrated optical-resolution (OR) and acoustic-resolution (AR) PAM system implemented by delivering light via an optical fiber bundle. A single fiber core is used to deliver light for OR illumination in order to achieve a small spot size and hence high lateral resolution, whereas all the fiber cores are used to deliver more energy for AR illumination. Most other components are shared by the OR and AR imaging. The lateral resolution can be seamlessly switched between 2.2 and 40 µm as the maximum imaging depth is switched between 1.3 and 3.0 mm. The system enables automatically coregistered higher-resolution OR and deeper AR photoacoustic imaging.

Video-rate functional photoacoustic microscopy at depths.

We report the development of functional photoacoustic microscopy capable of video-rate high-resolution in vivo imaging in deep tissue. A lightweight photoacoustic probe is made of a single-element broadband ultrasound transducer, a compact photoacoustic beam combiner, and a bright-field light delivery system. Focused broadband ultrasound detection provides a 44-µm lateral resolution and a 28-µm axial resolution based on the envelope (a 15-µm axial resolution based on the raw RF signal). Due to the efficient bright-field light delivery, the system can image as deep as 4.8 mm in vivo using low excitation pulse energy (28 µJ per pulse, 0.35 mJ/cm² on the skin surface). The photoacoustic probe is mounted on a fast-scanning voice-coil scanner to acquire 40 two-dimensional (2-D) B-scan images per second over a 9-mm range. High-resolution anatomical imaging is demonstrated in the mouse ear and brain. Via fast dual-wavelength switching, oxygen dynamics of mouse cardio-vasculature is imaged in realtime as well.