time-resolved reflectance measurements for the non-invasive determination of tissue optical properties Proc. SPIE 1064 97-106 Appl. Opt. 4 1504-9 of tissues and phantom materials at 633 nm Med. Phys. 14 835-41 cross section 3. Opt. Soc. Am. 55 16-21

One of the major factors that limits the treatment effectiveness for gliomas is the presence of the blood–brain barrier (BBB) which protects infiltrating glioma cells from the effects of anti-cancer agents. Circulating monocytes/macrophages (Ma) have a natural ability to traverse the intact and compromised BBB and loaded with anti cancer agents could be used as vectors to target tumors and surrounding tumor infiltrated tissue. Nanoshells (NS) are composed of a dielectric core (silica) coated with an ultrathin gold layer which converts absorbed near-infrared light (NIR) to heat with an extremely high efficacy and stability. We have investigated the effects of exposure to laser NIR on multicell human glioma spheroids infiltrated with empty (containing no nanoshells) or nanoshell loaded macrophages. Our results demonstrated that; (1) macrophages could efficiently take up bare or coated (PEGylated) gold NS: (2) NS loaded macrophages infiltrated into glioma spheroids to the same or, in some cases, to a greater degree than empty Ma; (3) NIR laser irradiation of spheroids incorporating NS loaded macrophages resulted in complete growth inhibition in an irradiance dependent manner, and (4) spheroids infiltrated with empty macrophages had growth curves identical to untreated control cultures. The results of this study provide proof of concept for the use of macrophages as a delivery vector of NS into gliomas for photothermal ablation and open the possibility of developing such regimens for patient treatment.

Site-specific delivery of nanoparticles poses a significant challenge, especially in the brain where the blood–brain barrier prevents the entry of most therapeutic compounds including nanoparticle-based anti-cancer agents. In this context, the use of macrophages as vectors for the delivery of gold–silica nanoshells to infiltrating gliomas will be reviewed in this article. Gold–silica nanoshells are readily phagocytosed by macrophages without any apparent toxic effects, and the results of in vitro studies have demonstrated the migratory potential of nanoshell-loaded macrophages in human glioma spheroids. Of particular interest is the observation that, after near-infrared exposure of spheroids containing nanoshell-loaded macrophages, sufficient heat was generated to suppress spheroid growth. Collectively, these findings demonstrate the potential of macrophages as nanoshell delivery vectors for photothermal therapy of gliomas, and they certainly provide the basis for future animal studies.

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Treatment with ALA PDT induced pronounced necrosis in tumors only if the light was delivered at a low rate. The treatment prolonged the survival for tumor-bearing animals.

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Gold-based nanoparticles have been used in a number of therapeutic and diagnostic applications. The purpose of this study was to investigate the efficacy of gold–silica nanoshells (AuNS) in photothermal therapy (PTT) of rat gliomas. Rat alveolar macrophages (Ma) were used as nanoparticle delivery vectors. Uptake of AuNS (bare and PEGylated) was investigated in Ma. AuNS were incubated with Ma for 24 h. Phase contrast microscopy was used to visualize the distribution of loaded Ma in three-dimensional glioma spheroids. PTT efficacy was evaluated for both empty (Ma) and AuNS-loaded Ma (MaNS) in both monolayers and spheroids consisting of C6 rat glioma cells and Ma. Monolayers/spheroids were irradiated for 5 min with light from an 810-nm diode laser at irradiances ranging from 7 to 28 W cm−2. Monolayer survival was evaluated using a 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS) assay while PTT efficacy in spheroids was determined from growth kinetics and live/dead fluorescence microscopy. PTT efficacy was investigated in vivo using a Sprague–Dawley rat glioma model. Five rats received direct intracranial injection of a mixture of 104 C6 glioma cells and, 2 days later, an equal number of MaNS. Three rats received laser treatment (810 nm; 10 min; 1 W) while the remaining two served as controls (no laser treatment). The uptake ratio of bare to PEGylated AuNS by Ma was 4:1. A significant photothermal effect was observed in vitro, albeit at relatively high radiant exposures (2.1–4.2 kJ cm−2). PTT proved effective in vivo in preventing or delaying tumor development in the PTT-treated animals.

The blood-brain barrier (BBB) poses a significant impediment for the delivery of therapeutic drugs into the brain. This is particularly problematic for the treatment of malignant gliomas which are characterized by diffuse infiltration of tumor cells into normal brain where they are protected by a patent BBB. Selective disruption of the BBB, followed by administration of anti-cancer agents, represents a promising approach for the elimination of infiltrating glioma cells. A summary of the techniques (focused ultrasound, photodynamic therapy and photochemical internalization) for site-specific opening of the BBB will be discussed in this review. Each approach is capable of causing localized and transient opening of the BBB with minimal damage to surrounding normal brain as evidenced from magnetic resonance images and histology. T1-weighted MRI contrast enhanced images (a, b) showing focal enhancement in the area of light treatment. Fluence levels of 9 (a) and 17 J (b) at a fluence rate of 10 mW were performed 4 h following ALA administration (125 mg kg−1 i.p.). Scans were acquired 3–4 h post-PDT and 15 min following i.p. Gd contrast administration. Coronal H&E sections (c, d) taken from the brains of Fischer rats 14 days post-treatment. No significant pathology was observed following delivery of 9 J (c). At the high fluence (17 J), extensive infiltration of lymphocytes and macrophages was apparent as shown by the arrow in (d) [19]. Reprinted with permission.