Purpose: Development of new therapeutic drug delivery systems is an area of significant research interest. The ability to directly target a therapeutic agent to a tumor site would minimize systemic drug exposure, thus providing the potential for increasing the therapeutic index. Experimental Design: Photodynamic therapy (PDT) involves the uptake of a sensitizer by the cancer cells followed by photoirradiation to activate the sensitizer. PDTusing Photofrin has certain disadvantages that include prolonged cutaneous photosensitization. Delivery of nanoparticles encapsulated with photodynamic agent specifically to a tumor site could potentially overcome the drawbacks of systemic therapy. In this study, we have developed a multifunctional polymeric nanoparticle consisting of a surface-localized tumor vasculature targeting F3 peptide and encapsulated PDTand imaging agents. Results:The nanoparticles specifically bound to the surface of MDA-435 cells in vitro and were internalized conferring photosensitivity to the cells. Significant magnetic resonance imaging contrast enhancement was achieved in i.c. rat 9L gliomas following i.v. nanoparticle administration. Serial magnetic resonance imaging was used for determination of pharmacokinetics and distribution of nanoparticles within the tumor. Treatment of glioma-bearing rats with targeted nanoparticles followed by PDT showed a significant improvement in survival rate when compared with animals who received PDT after administration of nontargeted nanoparticles or systemic Photofrin. Conclusions:This study reveals the versatility and efficacy of the multifunctional nanoparticle for the targeted detection and treatment of cancer.Photodynamic therapy (PDT) relies on the selective uptake of a photosensitizing molecule in a tumor relative to the surrounding normal parenchyma followed by exposure to the appropriate wavelength of light to activate the photosensitizer (1). When activated by light irradiation, the photosensitizer interacts with molecular oxygen to produce a cytotoxic, shortlived species known as singlet oxygen. PDT elicits both apoptotic and necrotic responses within treated tumors and produces microvascular injury leading to inflammation and hypoxia. Photofrin, a complex mixture of porphyrin oligomers, is one of the most efficient photosensitizers approved for PDT of cancer (2). However, Photofrin can cause prolonged skin photosensitization, where patients are required to avoid direct exposure to sunlight for a period of 4 to 6 weeks. Current strategies under development include attempts to direct the photosensitizing agent to the tumor by active targeting approaches, such as peptide conjugates and antibodies (3 -7), incorporation within liposomes (8, 9), and encapsulation within polymeric nanoparticles (10 -14) in an attempt to deliver higher local concentrations at the therapeutic site.A recent report of a sub-100 nm dynamic nanoparticle platform composed of polyacrylamide, which could be loaded with a photoactivatable agent (methylene blue) for the spe...

Optical PEBBLE (probes encapsulated by biologically localized embedding) nanosensors have been developed for dissolved oxygen using organically modified silicate (ormosil) nanoparticles as a matrix. The ormosil nanoparticles are prepared via a sol-gel-based process, which includes the formation of core particles with phenyltrimethoxysilane as a precursor followed by the formation of a coating layer with methyltrimethoxysilane as a precursor. The average diameter of the resultant particles is 120 nm. These sensors incorporate the oxygen-sensitive platinum porphyrin dye as an indicator and an oxygen-insensitive dye as a reference for ratiometric intensity measurement. Two pairs of indicator dye and reference dye, respectively, platinum(II) octaethylporphine and 3,3'-dioctadecyloxacarbocyanine perchlorate, and platinum(II) octaethylporphine ketone and octaethylporphine, were used. The sensors have excellent sensitivity with an overall quenching response of 97%, as well as excellent linearity of the Stern-Volmer plot (r(2) = 0.999) over the whole range of dissolved oxygen concentrations (0-43 ppm). In vitro intracellular changes of dissolved oxygen due to cell respiration were monitored, with gene gun injected PEBBLEs, in rat C6 glioma cells. A significant change was observed with a fluorescence ratio increase of up to 500% after 1 h, for nine different sets of cells, which corresponds to a 90% reduction in terms of dissolved oxygen concentration. These results clearly show the validity of the delivery method for intracellular studies of PEBBLE sensors, as well as the high sensitivity, which is needed to achieve real-time measurements of intracellular dissolved oxygen concentration.

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