A paintable phosphorescent bandage for postoperative tissue oxygen assessment in DIEP flap reconstruction.

Flaps are common in plastic surgery to reconstruct large tissue defects in cases such as trauma or cancer. However, most tissue oximeters used for monitoring ischemia in postoperative flaps are bulky, wired devices, which hinder direct flap observation. Here, we present the results of a clinical trial using a previously untried paintable transparent phosphorescent bandage to assess the tissue's partial pressure of oxygen (pO2). Statistical analysis revealed a strong relationship (P < 0.0001) between the rates of change of tissue oxygenation measured by the bandage and blood oxygen saturation (%stO2) readings from a standard-of-care ViOptix near-infrared spectroscopy oximeter. In addition, the oxygen-sensing bandage showed no adverse effects, proved easy handling, and yielded bright images across all skin tones with a digital single-lens reflex (DSLR) camera. This demonstrates the feasibility of using phosphorescent materials to monitor flaps postoperatively and lays the groundwork for future exploration in other tissue oxygen sensing applications.

Plasmonic Nanoparticle-Based Digital Cytometry to Quantify MUC16 Binding on the Surface of Leukocytes in Ovarian Cancer.

Although levels of the circulating ovarian cancer marker (CA125) can distinguish ovarian masses that are likely to be malignant and correlate with severity of disease, serum CA125 has not proved useful in general population screening. Recently, cell culture studies have indicated that MUC16 may bind to the Siglec-9 receptor on natural killer (NK) cells where it downregulates the cytotoxicity of NK cells, allowing ovarian cancer cells to evade immune surveillance. We present evidence that the presence of MUC16 can be locally visualized and imaged on the surface of peripheral blood mononuclear cells (PBMCs) in ovarian cancer via a novel "digital" cytometry technique that incorporates: (i) OC125 monoclonal antibody-conjugated gold nanoparticles as optical nanoprobes, (ii) a high contrast dark-field microscopy system to detect PBMC-bound gold nanoparticles, and (iii) a computational algorithm for automatic counting of these nanoparticles to estimate the quantity of surface-bound MUC16. The quantitative detection of our technique was successfully demonstrated by discriminating clones of the ovarian cancer cell line, OVCAR3, based on low, intermediate, and high expression levels of MUC16. Additionally, PBMC surface-bound MUC16 was tracked in an ovarian cancer patient over a 17 month period; the results suggest that the binding of MUC16 on the surface of immune cells may play an early indicator for recurrent metastasis 6 months before computational tomography-based clinical diagnosis. We also demonstrate that the levels of surface-bound MUC16 on PBMCs from five ovarian cancer patients were greater than those from five healthy controls.

Non-invasive monitoring of skin inflammation using an oxygen-sensing paint-on bandage.

Inflammation involves a cascade of cellular and molecular mediators that ultimately lead to the infiltration of immune cells into the affected area. This inflammatory process in skin is common to many diseases including acne, infection, and psoriasis, with the presence or absence of immune cells a potential diagnostic marker. Here we show that skin inflammation can be non-invasively measured and mapped using a paint-on oxygen sensing bandage in an in vivo porcine inflammation model. After injection of a known inflammatory agent, the bandage could track the increase, plateau, and decrease in oxygen consumption at the injury site over 7 weeks, as well as discern inflammation resultant from injection at various depths beneath the surface of the skin. Both the initial rate of pO2 change and the change in bandage pO2 at equilibration (CBP20) were found to be directly related to the metabolic oxygen consumption rate of the tissue in contact. Healthy skin demonstrated an initial pO2 decrease rate of 6.5 [Formula: see text], and CBP20 of 84 [Formula: see text]. Inflamed skin had a significantly higher initial consumption rate of 55 [Formula: see text], and a larger CBP20 of 140 [Formula: see text]. The change in the bandage pO2 before and after equilibration with tissue was found to correlate well with histological evidence of skin inflammation in the animals.

An Integrin-Targeted, Highly Diffusive Construct for Photodynamic Therapy.

Targeted antineoplastic agents show great promise in the treatment of cancer, having the ability to impart cytotoxicity only to specific tumor types. However, these therapies do not experience uniform uptake throughout tumors, leading to sub-lethal cell killing that can impart treatment resistance, and cause problematic off-target effects. Here we demonstrate a photodynamic therapy construct that integrates both a cyclic RGD moiety for integrin-targeting, as well as a 5 kDa PEG chain that passivates the construct and enables its rapid diffusion throughout tumors. PEGylation of the photosensitizer construct was found to prevent photosensitizer aggregation, boost the generation of cytotoxic reactive radical species, and enable the rapid uptake of the construct into cells throughout large (>500 µm diameter) 3D tumor spheroids. Replacing the cyclic RGD with the generic RAD peptide led to the loss of cellular uptake in 3D culture, demonstrating the specificity of the construct. Photodynamic therapy with the construct was successful in inducing cytotoxicity, which could be competitively blocked by a tenfold concentration of free cyclic RGD. This construct is a first-of-its kind theranostic that may serve as a new approach in our growing therapeutic toolbox.

PLGA nanoparticle encapsulation reduces toxicity while retaining the therapeutic efficacy of EtNBS-PDT in vitro.

Photodynamic therapy regimens, which use light-activated molecules known as photosensitizers, are highly selective against many malignancies and can bypass certain challenging therapeutic resistance mechanisms. Photosensitizers such as the small cationic molecule EtNBS (5-ethylamino-9-diethyl-aminobenzo[a]phenothiazinium chloride) have proven potent against cancer cells that reside within acidic and hypoxic tumour microenvironments. At higher doses, however, these photosensitizers induce "dark toxicity" through light-independent mechanisms. In this study, we evaluated the use of nanoparticle encapsulation to overcome this limitation. Interestingly, encapsulation of the compound within poly(lactic-co-glycolic acid) (PLGA) nanoparticles (PLGA-EtNBS) was found to significantly reduce EtNBS dark toxicity while completely retaining the molecule's cytotoxicity in both normoxic and hypoxic conditions. This dual effect can be attributed to the mechanism of release: EtNBS remains encapsulated until external light irradiation, which stimulates an oxygen-independent, radical-mediated process that degrades the PLGA nanoparticles and releases the molecule. As these PLGA-encapsulated EtNBS nanoparticles are capable of penetrating deeply into the hypoxic and acidic cores of 3D spheroid cultures, they may enable the safe and efficacious treatment of otherwise unresponsive tumour regions.

Bright, "Clickable" Porphyrins for the Visualization of Oxygenation under Ambient Light.

A new group of "clickable" and brightly emissive metalloporphyrins has been developed for the visualization of oxygenation under ambient light with the naked eye. These alkynyl-terminated compounds permit the rapid and facile synthesis of oxygen-sensing dendrimers through azide-alkyne click chemistry. With absorption maxima overlapping with the wavelengths of common commercial laser sources, they are readily applicable to biomedical imaging of tissue oxygenation. An efficient synthetic methodology, featuring the stable trimethylacetyl (pivaloyl) protecting group, is described for their preparation. A paint-on liquid bandage containing a new, click-synthesized porphyrin dendrimer has been used to map oxygenation across an ex vivo porcine skin burn model.