Nripen Chanda

Bombesin functionalized gold nanoparticles show in vitro and in vivo cancer receptor specificity.

Development of cancer receptor-specific gold nanoparticles will allow efficient targeting/optimum retention of engineered gold nanoparticles within tumors and thus provide synergistic advantages in oncology as it relates to molecular imaging and therapy. Bombesin (BBN) peptides have demonstrated high affinity toward gastrin-releasing peptide (GRP) receptors in vivo that are overexpressed in prostate, breast, and small-cell lung carcinoma. We have synthesized a library of GRP receptor-avid nanoplatforms by conjugating gold nanoparticles (AuNPs) with BBN peptides. Cellular interactions and binding affinities (IC50) of AuNP–BBN conjugates toward GRP receptors on human prostate cancer cells have been investigated in detail. In vivo studies using AuNP–BBN and its radiolabeled surrogate 198AuNP–BBN, exhibiting high binding affinity (IC50 in microgram ranges), provide unequivocal evidence that AuNP–BBN constructs are GRP-receptor-specific showing accumulation with high selectivity in GRP-receptor-rich pancreatic acne in normal mice and also in tumors in prostate-tumor-bearing, severe combined immunodeficient mice. The i.p. mode of delivery has been found to be efficient as AuNP–BBN conjugates showed reduced RES organ uptake with concomitant increase in uptake at tumor targets. The selective uptake of this new generation of GRP-receptor-specific AuNP–BBN peptide analogs has demonstrated realistic clinical potential in molecular imaging via x-ray computed tomography techniques as the contrast numbers in prostate tumor sites are severalfold higher as compared to the pretreatment group (Hounsfield unit = 150).

Laminin receptor specific therapeutic gold nanoparticles (198AuNP-EGCg) show efficacy in treating prostate cancer

Systemic delivery of therapeutic agents to solid tumors is hindered by vascular and interstitial barriers. We hypothesized that prostate tumor specific epigallocatechin-gallate (EGCg) functionalized radioactive gold nanoparticles, when delivered intratumorally (IT), would circumvent transport barriers, resulting in targeted delivery of therapeutic payloads. The results described herein support our hypothesis. We report the development of inherently therapeutic gold nanoparticles derived from the Au-198 isotope; the range of the 198Au β-particle (approximately 11 mm in tissue or approximately 1100 cell diameters) is sufficiently long to provide cross-fire effects of a radiation dose delivered to cells within the prostate gland and short enough to minimize the radiation dose to critical tissues near the periphery of the capsule. The formulation of biocompatible 198AuNPs utilizes the redox chemistry of prostate tumor specific phytochemical EGCg as it converts gold salt into gold nanoparticles and also selectively binds with excellent affinity to Laminin67R receptors, which are over expressed in prostate tumor cells. Pharmacokinetic studies in PC-3 xenograft SCID mice showed approximately 72% retention of 198AuNP-EGCg in tumors 24 h after intratumoral administration. Therapeutic studies showed 80% reduction of tumor volumes after 28 d demonstrating significant inhibition of tumor growth compared to controls. This innovative nanotechnological approach serves as a basis for designing biocompatible target specific antineoplastic agents. This novel intratumorally injectable 198AuNP-EGCg nanotherapeutic agent may provide significant advances in oncology for use as an effective treatment for prostate and other solid tumors.

Radioactive gold nanoparticles in cancer therapy: therapeutic efficacy studies of GA-198AuNP nanoconstruct in prostate tumor–bearing mice

UNLABELLED Biocompatibility studies and cancer therapeutic applications of nanoparticulate beta-emitting gold-198 (198Au; beta(max) = 0.96 MeV; half-life of 2.7 days) are described. Gum arabic glycoprotein (GA)-functionalized gold nanoparticles (AuNPs) possess optimum sizes (12-18 nm core diameter and 85 nm hydrodynamic diameter) to target individual tumor cells and penetrate through tumor vasculature and pores. We report the results of detailed in vivo therapeutic investigations demonstrating the high tumor affinity of GA-198AuNPs in severely compromised immunodeficient (SCID) mice bearing human prostate tumor xenografts. Intratumoral administration of a single dose of beta-emitting GA-198AuNPs (70 Gy) resulted in clinically significant tumor regression and effective control in the growth of prostate tumors over 30 days. Three weeks after administration of GA-198AuNPs, tumor volumes for the treated animals were 82% smaller as compared with tumor volume of control group. The treatment group showed only transitory weight loss in sharp contrast to the tumor-bearing control group, which underwent substantial weight loss. Pharmacokinetic studies have provided unequivocal evidence for the optimum retention of therapeutic payload of GA-198AuNPs within the tumor site throughout the treatment regimen with minimal or no leakage of radioactivity to various nontarget organs. The measurements of white and red blood cells, platelets, and lymphocytes within the treatment group resembled those of the normal SCID mice, thus providing further evidence on the therapeutic efficacy and concomitant in vivo tolerance and nontoxic features of GA-198AuNPs. FROM THE CLINICAL EDITOR In this study, the biocompatibility and cancer therapeutic applications of glycoprotein (GA) functionalized gold nanoparticles containing b-emitting Au-198 are described in SCID mice bearing human prostate tumor xenografts. The findings of significant therapeutic efficacy, good in vivo tolerance and non-toxic features make these particles ideal candidates for future human applications.

Gastrin releasing protein receptor specific gold nanorods: Breast and Prostate tumor avid nanovectors for molecular imaging

Gastrin releasing protein receptor specific bombesin (BBN) peptide-gold nanoconjugates were successfully synthesized using gold nanorods and dithiolated peptide. The gold nanorod-bombesin (GNR-BBN) conjugates showed extraordinary in vitro stabilities against various biomolecules including NaCl, cysteine, histidine, bovine serum albumin, human serum albumin, and dithiothreitol. Quantitative measurements on the binding affinity (IC(50)) of GNR-BBN conjugates toward prostate and breast tumor cells were evaluated. The IC(50) values establish that GNR-BBN conjugates have strong affinity toward the gastrin releasing peptide receptors on both the tumors. Detailed cellular interaction studies of GNR-BBN conjugates revealed that nanorods internalize via a receptor-mediated endocytosis pathway. The receptor specific interactions of GNR-BBN conjugates provide realistic opportunities in the design and development of in vivo molecular imaging and therapy agents for cancer.

Gold Nanoparticle Contrast in a Phantom and Juvenile Swine : Models for Molecular Imaging of Human Organs using X-ray Computed Tomography

RATIONALE AND OBJECTIVES The purpose of this study was to demonstrate the application of gold nanoparticles (AuNP) as a contrast agent for a clinical x-ray computed tomography (CT) system using a phantom and juvenile swine. MATERIALS AND METHODS A tissue-mimicking phantom with spherical inclusions containing known concentrations of Au was scanned. Swine were injected with gum Arabic stabilized Au nanoparticles (GA-AuNP), up to 85 mg kg(-1) body weight. CT scans were performed before and after the injections. Changes in Hounsfield unit (HU) values between pre- and post- injection scans were evaluated and compared to postmortem determinations of Au uptake. Average uptake of GA-AuNP in the liver of the swine was 380 microg per gram of liver and 680 microg per gram of spleen. RESULTS Concentrations of Au in tissues increased the CT numbers in liver by approximately 22 HU per mg Au concentration at 80 kVp and 27 HU per mg Au concentration at 140 kVp. These data were consistent with HU changes observed for similar concentrations in the phantom. CONCLUSIONS AuNP-based contrast agents may be useful in x-ray based CT. This study provides data for determining concentrations of AuNP in comparison to other contrast materials.

An Effective Strategy for the Synthesis of Biocompatible Gold Nanoparticles Using Cinnamon Phytochemicals for Phantom CT Imaging and Photoacoustic Detection of Cancerous Cells

ABSTRACTPurposeThe purpose of the present study was to explore the utilization of cinnamon-coated gold nanoparticles (Cin-AuNPs) as CT/optical contrast-enhancement agents for detection of cancer cells.MethodsCin-AuNPs were synthesized by a “green” procedure, and the detailed characterization was performed by physico-chemical analysis. Cytotoxicity and cellular uptake studies were carried out in normal human fibroblast and cancerous (PC-3 and MCF-7) cells, respectively. The efficacy of detecting cancerous cells was monitored using a photoacoustic technique. In vivo biodistribution was studied after IV injection of Cin-AuNPs in mice, and also a CT phantom model was generated.ResultsBiocompatible Cin-AuNPs were synthesized with high purity. Significant uptake of these gold nanoparticles was observed in PC-3 and MCF-7 cells. Cin-AuNPs internalized in cancerous cells facilitated detectable photoacoustic signals. In vivo biodistribution in normal mice showed steady accumulation of gold nanoparticles in lungs and rapid clearance from blood. Quantitative analysis of CT values in phantom model revealed that the cinnamon-phytochemical-coated AuNPs have reasonable attenuation efficiency.ConclusionsThe results indicate that these non-toxic Cin-AuNPs can serve as excellent CT/ photoacoustic contrast-enhancement agents and may provide a novel approach toward tumor detection through nanopharmaceuticals.

Functionalized radioactive gold nanoparticles in tumor therapy

The development of new treatment modalities that offer clinicians the ability to reduce sizes of tumor prior to surgical resection or to achieve complete ablation without surgery would be a significant medical breakthrough in the overall care and treatment of prostate cancer patients. The goal of our investigation is aimed at validating the hypothesis that Gum Arabic-functionalized radioactive gold nanoparticles (GA-(198) AuNP) have high affinity toward tumor vasculature. We hypothesized further that intratumoral delivery of the GA-(198) AuNP agent within prostate tumor will allow optimal therapeutic payload that will significantly or completely ablate tumor without side effects, in patients with hormone refractory prostate cancer. In order to evaluate the therapeutic efficacy of this new nanoceutical, GA-(198) AuNP was produced by stabilization of radioactive gold nanoparticles ((198) Au) with the FDA-approved glycoprotein, GA. This review will describe basic and clinical translation studies toward realization of the therapeutic potential and myriad of clinical applications of GA-(198) AuNP agent in treating prostate and various solid tumors in human cancer patients.

Bombesin Peptide Conjugated Gold Nanocages Internalize via Clathrin Mediated Endocytosis

The nature of interaction and mechanism of internalization of receptor-avid peptide nanoparticles with cells is not yet completely understood. This article describes the cellular internalization mechanism and intracellular trafficking of peptide conjugated receptor targeted porous Gold nanocages (AuNCs) in cancer cells. We synthesized and characterized a library of AuNCs conjugated with bombesin (BBN) peptide. Evidence of selective affinity of AuNC-BBN toward gastrin releasing peptide receptors (GRPR) was obtained using radiolabeled competitive cell binding assay. Endocytic mechanism was investigated using cell inhibitor studies and monitored using optical and transmission electron microscopy (TEM). Results show AuNC-BBN uptake in PC3 cells is mediated by clathrin mediated endocytosis (CME). Indeed, in the presence of CME inhibitors, AuNC-BBN uptake in cells is reduced up to 84%. TEM images further confirm CME characteristic clathrin coated pits and lysosomal release of AuNCs. These results demonstrate that peptide ligands conjugated to the surface of nanoparticles maintain their target specificity. This bolsters the case for peptide robustness and its persisting functionality in intracellular vehicular delivery systems.

Nanoparticles and Phage Display Selected Peptides for Imaging and Therapy of Cancer

Molecular imaging probes are a special class of pharmaceuticals that target specific biochemical signatures associated with disease and allow for noninvasive imaging on the molecular level. Because changes in biochemistry occur before diseases reach an advanced stage, molecular imaging probes make it possible to locate and stage disease, track the effectiveness of drugs, treat disease, monitor response, and select patients to allow for more personalized diagnosis and treatment of disease. Targeting agents radiolabeled with positron emitters are of interest due to their ability to quantitatively measure biodistribution and receptor expression to allow for optimal dose determinations. (68)Ga is a positron emitter, which allows for quantitative imaging through positron emission chromatography (PET). The availability of (68)Ga from a generator and its ability to form stable complexes with a variety of chelates hold promise for expanding PET utilization to facilities unable to afford their own cyclotron. Nanoparticles conjugated with various proteins and peptides derived from phage display that can be selectively targeted are being developed and evaluated for guided imaging and therapy. Herein we highlight some initial efforts in combining the enhanced selectivity of nanoparticles and peptides with (68)Ga for use as molecular imaging probes.

Novel nanochemistry toward generation and stabilization of gold nanoparticles in human serum albumin matrix

The interactions of gold nanoparticles (AuNPs) with human serum albumin (HSA) greatly influence their in vivo characteristics. It is important to develop conjugates that can serve as ideal structural models to understand the interaction of AuNPs with HSA. We report the synthesis and stabilization of AuNPs in HSA matrix with no additional ligands on the surface of the NPs. The hydrodynamic size of the AuNP–HSA conjugate is 22 nm, and transmission electron microscopy (TEM) measurement shows the core size as 8–13 nm. We have performed strip assay to establish that the biological activity of HSA is retained even after conjugation. Our cellular toxicity evaluation studies show that AuNP–HSA conjugates are nontoxic and biocompatible.