Mithun M. Shenoi

Nanoparticle delivered vascular disrupting agents (VDAs): use of TNF-alpha conjugated gold nanoparticles for multimodal cancer therapy.

Surgery, radiation and chemotherapy remain the mainstay of current cancer therapy. However, treatment failure persists due to the inability to achieve complete local control of the tumor and curtail metastatic spread. Vascular disrupting agents (VDAs) are a class of promising systemic agents that are known to synergistically enhance radiation, chemotherapy or thermal treatments of solid tumors. Unfortunately, there is still an unmet need for VDAs with more favorable safety profiles and fewer side effects. Recent work has demonstrated that conjugating VDAs to other molecules (polyethylene glycol, CNGRCG peptide) or nanoparticles (liposomes, gold) can reduce toxicity of one prominent VDA (tumor necrosis factor alpha, TNF-α). In this report, we show the potential of a gold conjugated TNF-α nanoparticle (NP-TNF) to improve multimodal cancer therapies with VDAs. In a dorsal skin fold and hindlimb murine xenograft model of prostate cancer, we found that NP-TNF disrupts endothelial barrier function and induces a significant increase in vascular permeability within the first 1-2 h followed by a dramatic 80% drop in perfusion 2-6 h after systemic administration. We also demonstrate that the tumor response to the nanoparticle can be verified using dynamic contrast-enhanced magnetic resonance imaging (MRI), a technique in clinical use. Additionally, multimodal treatment with thermal therapies at the perfusion nadir in the sub- and supraphysiological temperature regimes increases tumor volumetric destruction by over 60% and leads to significant tumor growth delays compared to thermal therapy alone. Lastly, NP-TNF was found to enhance thermal therapy in the absence of neutrophil recruitment, suggesting that immune/inflammatory regulation is not central to its power as part of a multimodal approach. Our data demonstrate the potential of nanoparticle-conjugated VDAs to significantly improve cancer therapy by preconditioning tumor vasculature to a secondary insult in a targeted manner. We anticipate our work to direct investigations into more potent tumor vasculature specific combinations of VDAs and nanoparticles with the goal of transitioning optimal regimens into clinical trials.

Use of Tumor Necrosis Factor–alpha-coated Gold Nanoparticles to Enhance Radiofrequency Ablation in a Translational Model of Renal Tumors

OBJECTIVES Radiofrequency ablation (RFA) has been most effective when the tumors are small, exophytic, and away from vital structures. We enlarged the size of the ablation kill zone by infusing a 30-nm tumor necrosis factor-alpha and polyethylene glycol-coated gold nanoparticle (CYT-6091, CytImmune Sciences, Inc.) before ablation in a rabbit kidney tumor model. MATERIALS AND METHODS A total of 37 New Zealand White rabbits had VX-2 tumors implanted into their bilateral kidneys; they were then split into 3 treatment groups of 10 rabbits each and a sham group of 7 rabbits as follows: (1) CYT-6091 only, (2) RFA only, (3) CYT-6091 followed 4 hours later by RFA. Gross and microscopic measurements of the ablation size as well as histologic analysis using hematoxylin and eosin staining were performed to determine the effect of CYT-6091 on the ablation. RESULTS The RFA + CYT-6091 group had a larger zone of complete cell death than the RFA-only group when measured on microscopic examination (0.30 +/- 0.07 vs 0.23 +/- 0.03 mL, P = .03). The zone of partially ablated tissue was smaller in the RFA + CYT-6091 group than in the RFA-only group (0.08 +/- 0.02 vs 0.13 +/- 0.05 mL, P = .01). CONCLUSIONS We have demonstrated the efficacy of CYT-6091 in enhancing RFA in a translational kidney tumor model. The potential usage of CYT-6091 to improve RFA of renal cell carcinoma merits further study.

Concentration and volume effects in thermochemical ablation in vivo: Results in a porcine model

Purpose: To explore the effects of volume and concentration in thermochemical ablation using an in vivo porcine model. Methods: Twelve swine 60–75 kg were used in this institutionally approved study. A needle design prototype coaxial device for reagent injections and a thermocouple were inserted into surgically exposed liver. Simultaneously, an acid and base (acetic acid and NaOH) were injected at 4 mL/min based on a 3 × 3 matrix with concentration (5, 10, and 15 mol/L) and volume on the axes (total volumes of 1, 2, and 4 mL). Three animals (centre grid position) strengthened the statistical analysis. Each animal received four identical injections (total 48). Temperatures and heart rate were recorded. Livers were formalin-fixed after sacrifice. After sectioning, coagulation zones were analysed by two observers. Area and slice thickness were used to calculate the volume, surface area, and sphericity for each treatment. Results: Coagulation volumes ranged from 2.95 ± 0.29 to 14.72 ± 1.42 mL with a maximum of 18.3 mL. Highest peak temperature was 105°C with temperatures ranging 43.5 ± 2.6°C to 91.0 ± 6.5°C. There was no association between conditions and sphericity or heart rate. Conclusions: The method can be used successfully to ablate tissue in vivo. By neutralising acid in situ and releasing heat and a salt, this technique improves considerably upon the use of acetic acid used alone. Peak temperatures exceeded accepted coagulation thresholds even if the only mechanism operating was hyperthermia. Reagent concentrations and volumes increased the amount of the coagulum but not in a linear fashion.

In vivo comparison of simultaneous versus sequential injection technique for thermochemical ablation in a porcine model

Purpose: To investigate simultaneous and sequential injection thermochemical ablation in a porcine model, and compare them to sham and acid-only ablation. Materials and methods: This IACUC-approved study involved 11 pigs in an acute setting. Ultrasound was used to guide placement of a thermocouple probe and coaxial device designed for thermochemical ablation. Solutions of 10 M acetic acid and NaOH were used in the study. Four injections per pig were performed in identical order at a total rate of 4 mL/min: saline sham, simultaneous, sequential, and acid only. Volume and sphericity of zones of coagulation were measured. Fixed specimens were examined by H&E stain. Results: Average coagulation volumes were 11.2 mL (simultaneous), 19.0 mL (sequential) and 4.4 mL (acid). The highest temperature, 81.3°C, was obtained with simultaneous injection. Average temperatures were 61.1°C (simultaneous), 47.7°C (sequential) and 39.5°C (acid only). Sphericity coefficients (0.83–0.89) had no statistically significant difference among conditions. Conclusions: Thermochemical ablation produced substantial volumes of coagulated tissues relative to the amounts of reagents injected, considerably greater than acid alone in either technique employed. The largest volumes were obtained with sequential injection, yet this came at a price in one case of cardiac arrest. Simultaneous injection yielded the highest recorded temperatures and may be tolerated as well as or better than acid injection alone. Although this pilot study did not show a clear advantage for either sequential or simultaneous methods, the results indicate that thermochemical ablation is attractive for further investigation with regard to both safety and efficacy.

Nanoparticle enhanced thermal therapies

Thermal therapies such as hyperthermia, radiofrequency ablation, cryoablation, etc. have shown great potential and are gaining increasing clinical acceptance in the treatment of solid tumors. However, these treatment modalities are limited by the size of tumor that can be treated, incomplete tumor kill, and damage to adjacent normal tissues. To address these limitations, the concept of adjuvant-assisted thermal therapies has been proposed and tested to enhance the tumor destructive effects of thermal therapies. CYT-6091, a pegylated colloidal gold nanoparticle containing TNF-alpha bound to its surface, has been extensively investigated in our lab as an adjuvant to enhance thermal therapies. This paper describes our investigations of nanoparticle enhanced thermal therapies in various preclinical and translational models of solid tumors.

Label-Free CMOS DNA Quantification with On-Chip Noise Reduction Schemes

We present a label-free CMOS DNA sensor with a new sensing-pixel architecture and background noise reduction scheme. The proposed sensor generates a differential signal between bio-samples and reference buffer solution with significant reduction in offset and gain fixed pattern noise by employing on-chip correlated double sampling circuits. Non-surface-binding detection technique allows to quantify DNA molecules continuously and sequentially and to reuse the sensor by simple washing protocol. By directly reading the negative charges of DNA molecules, DNA concentrations from 1 muM to 10 muM have been successfully discriminated.

In vivo detection of the effects of preconditioning on LNCaP tumors by a TNF-α nanoparticle construct using MRI.

The outcome of systemic and local therapies (e.g. chemotherapy, radiotherapy, surgery, focal ablation) for prostate cancer can be significantly improved by using tumor‐specific adjuvants prior to treatment (“preconditioning”). We propose to use dynamic contrast enhanced magnetic resonance imaging (DCE‐MRI) to monitor the in vivo response of a mouse model of prostate cancer treated with a vascular disruptive agent, TNF‐α, delivered on a gold nanoparticle (NP‐TNF). Six male nude mice bearing 4–5 week old LNCaP tumors were scanned at 9.4 T. DCE‐MRI was performed two days before and 4–5 h after treatment with NP‐TNF. An intraperitoneal (i.p.) bolus of gadolinium‐DTPA (Gd) was administered and contrast enhancement was measured for 90 min. Concentration–time curves of Gd were calculated and the area under the Gd curve (AUGC) was determined pre‐ and post‐treatment. NP‐TNF treatment caused an increase in contrast uptake in tumors. Interestingly, the early concentration (10 min post Gd bolus i.p.) was similar in both untreated and treated conditions; however, 90 min after injection, [Gd] was 3.4 times higher than before treatment. AUGC doubled from (11 ± 6) [Gd] × min before treatment to (22 ± 9) [Gd] × min after treatment. An increase in signal enhancement was also observed in the muscle but to a lesser degree. We also evaluated the kinetics of intravenous Gd administration in mice bearing a jugular vein catheter to mimic the delivery method used in clinical trials. The overall treatment effects were independent of the delivery pathway of the contrast agent. In conclusion, we show that DCE‐MRI is suitable to detect changes associated with a vascular disruptive agent in a mouse model of prostate cancer. The ability to characterize the effects of nanoparticle therapy in vivo with non‐destructive methods is important, as such compounds, in combination with treatment strategies, are progressing towards clinical trials. Copyright

CT Visualization and Histopathological Assessment of Cryoablation in Pulmonary Veins

Over 2 million adults in the United States are affected by atrial fibrillation (AF), a common cardiac arrhythmia that is associated with decreased survival, increased cardiovascular morbidities, and a decrease in quality of life. Atrial fibrillation can be initiated by ectopic beats originating in the myocardial sleeves surrounding the pulmonary veins [1]. Pulmonary vein (PV) isolation via radiofrequency ablation is the current gold standard for treating patients with drug-refractory AF [2]. However, cryoablation is emerging as a new minimally-invasive technique to achieve PV isolation. Cryoablation is fast gaining acceptance due to its minimal tissue disruption, decreased thrombogenicity, and reduced complications (RF can lead to low rate of pulmonary vein stenosis) [2]. One important question in regard to this technology is whether the PV lesion is transmural and circumferential and to what extent adjacent tissues are involved in the freezing process. As ice formation lends itself to image contrast in the body, we hypothesized that intraprocedural CT visualization of the iceball formation would allow us to predict the extent of the cryolesion and/or provide us with a measure of the adjacent tissue damage.Copyright

Multi-Probe Cryosurgical Configurations Extract Significantly Less Energy per Probe Than Single Probe Configurations: Implications for Clinical Cryosurgery

In the present study, the interaction between different cryoprobes was investigated in multi-probe configurations. Using a careful experimental and computational approach we show here that the ability of a single probe to cool (i.e. the cooling power of a probe governed by convective cooling of the cryogen within the probe) is greatly reduced in a simple dual probe configuration with 1.0–2.0 cm separation of these probes over the single probe case. One approach that shows promise for predicting multi-probe performance is the use of a “weighting factor” that governs this loss of cooling power in a given probe.Copyright