Ultrasound-activated decafluoropentane/chitosan nanodroplets effectively release oxygen to the skin.

It is first confirmed that it is important to take SOS inhomogeneities into account in high resolution PA tomography. The iterative reconstruction algorithms, that model acoustic refractive effects, in reconstructing SOS distributions, and subsequently using these distributions to correct PA tomograms, yield artifact-free highly accurate images. The approach of using the hybrid measurement method and the new reconstruction algorithms is successful in substantially improving the quality of PA images with a minimization of blurring and artifacts.

Perfluoropentane (PFP)-based oxygen-loaded nanobubbles (OLNBs) were previously proposed as adjuvant therapeutic tools for pathologies of different etiology sharing hypoxia as a common feature, including cancer, infection, and autoimmunity. Here we introduce a new platform of oxygen nanocarriers, based on 2H,3H-decafluoropentane (DFP) as core fluorocarbon. These new nanocarriers have been named oxygen-loaded nanodroplets (OLNDs) since DFP is liquid at body temperature, unlike gaseous PFP. Dextran-shelled OLNDs, available either in liquid or gel formulations, display spherical morphology, ~600 nm diameters, anionic charge, good oxygen carrying capacity, and no toxic effects on human keratinocytes after cell internalization. In vitro OLNDs result more effective in releasing oxygen to hypoxic environments than former OLNBs, as demonstrated by analysis through oxymetry. In vivo, OLNDs effectively enhance oxy-hemoglobin levels, as emerged from investigation by photoacoustic imaging. Interestingly, ultrasound (US) treatment further improves transdermal oxygen release from OLNDs. Taken together, these data suggest that US-activated, DFP-based OLNDs might be innovative, suitable and cost-effective devices to topically treat hypoxia-associated pathologies of the cutaneous tissues.

We present a "hybrid" imaging approach which can image both light absorption properties and acoustic transmission properties of an object in a two-dimensional slice using a computed tomography (CT) photoacoustic imager. The ultrasound transmission measurement method uses a strong optical absorber of small cross-section placed in the path of the light illuminating the sample. This absorber, which we call a passive element acts as a source of ultrasound. The interaction of ultrasound with the sample can be measured in transmission, using the same ultrasound detector used for photoacoustics. Such measurements are made at various angles around the sample in a CT approach. Images of the ultrasound propagation parameters, attenuation and speed of sound, can be reconstructed by inversion of a measurement model. We validate the method on specially designed phantoms and biological specimens. The obtained images are quantitative in terms of the shape, size, location, and acoustic properties of the examined heterogeneities.

Detection of tumor metastases in the lymphatic system is essential for accurate staging of malignancies. Commercially available superparagmagnetic nanoparticles (SPIOs) accumulate in normal lymph tissue after injection at a tumor site, whereas less or no accumulation takes place in metastatic nodes, thus enabling lymphatic staging using MRI. We verify for the first time the potential of SPIOs, such as Endorem(®) as a novel photoacoustic (PA) contrast agent in biological tissue. We injected five Wistar rats subcutaneously with variable amounts of Endorem(®) and scanned the resected lymph nodes using a tomographic PA setup. Findings were compared using histology, vibrating sample magnetometry (VSM) and 14 T MR-imaging. Our PA setup was able to detect the iron oxide accumulations in all the nodes containing the nanoparticles. The distribution inside the nodes corresponded with both MRI and histological findings. VSM revealed that iron quantities inside the nodes varied between 51 ± 4 and 11 ± 1 µg. Nodes without SPIO enhancement did not show up in any of the PA scans. Iron oxide nanoparticles (Endorem(®)) can be used as a PA contrast agent for lymph node analysis and a distinction can be made between nodes with and nodes without the agent. This opens up possibilities for intra-operative nodal staging for patients undergoing nodal resections for metastatic malignancies.