Andre M. Gobin

Enhanced drug delivery via hyperthermal membrane disruption using targeted gold nanoparticles with PEGylated Protein-G as a cofactor

UNLABELLEDnGold nanoparticles (GNPs) with near infrared (NIR) plasmon resonance have been promisingly used in photothermal cancer therapy as a less invasive treatment. Recombinant Protein-G (ProG) was PEGylated to act as a cofactor to immobilize immunoglobulins (IgGs) on GNPs by the Fc region, resulting in optimal orientation of IgGs for efficient cancer targeting. In-vitro studies showed that HER-2 overexpressing breast cancer cells, SK-BR-3, were efficiently targeted and ablated at a laser power of 900 J/cm(2) (5 W/cm(2) for 3 min). However, as a means of enhancing treatment efficacy by increasing cellular sensitivity to chemotherapeutic agents, we showed that GNP exposure to lower power laser resulted in small disruptions of cell membrane due to localized hyperthermia. This did not lead to cell death but provided a mechanism for killing cancer cells by providing enhanced uptake of drug molecules thus leading to a new avenue for hyperthermia-anticancer drug combined cancer therapeutics.nnnFROM THE CLINICAL EDITORnPEGylated recombinant Protein-G was used as a cofactor to optimize the orientation of IgGs providing target seeking properties to gold nanoparticles used in photothermal cancer therapy. The system demonstrated excellent properties in cancer therapy, with the hope and expectation of future clinical translation.

Tunability and stability of gold nanoparticles obtained from chloroauric acid and sodium thiosulfate reaction

In the quest for producing an effective, clinically relevant therapeutic agent, scalability, repeatability, and stability are paramount. In this paper, gold nanoparticles (GNPs) with precisely controlled near-infrared (NIR) absorption are synthesized by a single-step reaction of HAuCl4 and Na2S2O3 without assistance of additional templates, capping reagents, or seeds. The anisotropy in the shape of gold nanoparticles offers high NIR absorption, making it therapeutically relevant. The synthesized products consist of GNPs with different shapes and sizes, including small spherical colloid gold particles and non-spherical gold crystals. The NIR absorption wavelengths and particle size increase with increasing molar ratio of HAuCl4/Na2S2O3. Non-spherical gold particles can be further purified and separated by centrifugation to improve the NIR-absorbing fraction of particles. In-depth studies reveal that GNPs with good structural and optical stability only form in a certain range of the HAuCl4/Na2S2O3 molar ratio, whereas higher molar ratios result in unstable GNPs, which lose their NIR absorption peak due to decomposition and reassembly via Ostwald ripening. Tuning the optical absorption of the gold nanoparticles in the NIR regime via a robust and repeatable method will improve many applications requiring large quantities of desired NIR-absorbing nanoparticles.

Targeted Cancer Therapy by Immunoconjugated Gold–Gold Sulfide Nanoparticles Using Protein G as a Cofactor

Gold–gold sulfide nanoparticles (GGS-NPs) fabricated from chloroauric acid and sodium thiosulfate show unique near infrared (NIR) absorption that renders them as a promising candidate for photothermal cancer therapy. To improve targeting efficiency, we developed a versatile method to allow ordered immunoconjugation of antibodies on the surfaces of these nanoparticles via a PEGylated recombinant Protein G (ProG). The PEGylated ProG was prepared with orthopyridyldisulfide-polyethylene glycol-succinimidyl valerate, average MW 2000 (OPSS-PEG-SVA), to first allow the self-assembly of ProG on the nanoparticles, subsequently antibodies were added to this construct to enable active targeting. The bioconjugated GGS-NPs were characterized by TEM, NIR-spectra, dynamic light scattering and modified immunoassay. In in vitro studies, the ProG-conjugated GGS-NPs with bound mouse anti c-erbB-2 (HER-2) immunoglobulin G (IgG) successfully targeted the HER-2 overexpressing breast cancer cell, SK-BR-3. Extensive cell death was observed for the targeted SK-BR-3 line at a low laser power of 540xa0J (3xa0Wxa0cm−2 for 3xa0min) while the control breast cancer cell (low expressing HER-2), HTB-22 survived. Using PEGylated ProG as a cofactor for immobilization of antibodies offers a promising strategy to functionalize various IgGs on nanoparticles for engineering their biomedical applications in cancer therapeutics.

Gold/Chitosan nanocomposites with specific near infrared absorption for photothermal therapy applications

Gold/chitosan nanocomposites were synthesized and evaluated as a therapeutic agent for the photothermal therapy. Gold nanoparticles (Au NPs) with controllable optical absorption in the near infrared (NIR) region were prepared by the reaction of chloroauric acid and sodium thiosulfate. To apply these particles to cancer therapy, the bare Au NPs were coated with chitosan (CS), O-carboxymethyl chitosan (CMCS), and a blend of CS and CMCS for utilizations in physiologic conditions. The surface properties, optical stability, and photothermal ablation efficiency on hepatocellular carcinoma cells (HepG2) and human dermal fibroblast cells (HDF) demonstrate that these gold nanocomposites have great potential as a therapeutic agent in in vitro tests. The CS-coated nanocomposites show the highest efficiency for the photo-ablation on the HepG2 cells, and the CS and CMCS blended coated particles show the best discrimination between the cancer cell and normal cells. The well-controlled NIR absorption and the biocompatible surface of these nanocomposites allow low-power NIR laser activation and low-dosage particle injection for the cancer cell treatment.

A high yield, one-pot dialysis-based process for self-assembly of near infrared absorbing gold nanoparticles

HYPOTHESISnA facile, dialysis-based synthesis of stable near infrared (nIR) absorbing plasmonic gold nanoparticles (λmax=650-1000 nm) will increase the yield of nIR particles and reduce the amount of gold colloid contaminant in the product mixture.nnnEXPERIMENTSnChloroauric acid and sodium thiosulfate were reacted using a dialysis membrane as a reaction vessel. Product yield and composition was determined and compared to traditional synthesis methods. The product particle distribution, yield, and partitioning of gold between dispersed product and membrane-adsorbed gold were determined.nnnFINDINGSnThe synthesis results in polydisperse particle suspensions comprised of 70% spheroid-like particles, 27% triangular plates, and 3% rod-like structures with a 3% batch-to-batch variation and a prominent nIR absorption band with λmax=650-1000 nm. The amount of small gold colloid (λmax=530 nm; d<10 nm) in the isolated product was reduced by 96% compared to traditional methods. Additionally, 91.1% of the gold starting material is retained in the solution-based nanoparticle mixture while 8.2% is found on the dialysis membrane. The synthesis results in a quality ratio (QR=Abs(nIR)/Abs(530)) of 1.7-2.4 (twice that of previous techniques) and 14.3 times greater OD∗ml yield of the nIR-absorbing nanoparticle fraction.

A high yield, controllable process for producing tunable near infrared-absorbing gold nanoplates†

The purpose of this study was to optimize a new synthesis technique, “DiaSynth,” to produce near-infrared (nIR) absorbing gold nanoplates with prescribed localized surface plasmon resonance (LSPR) wavelengths in higher yields over conventional synthesis methods without the need for laborious purification steps. The molecular weight cut off (MWCO; 3.5, 8, 12, 15, 25 & 50 kDa) of the regenerated cellulose membranes (RCM), temperature (25, 37, 50 & 100 °C) and surface area to volume (SA/Vol) ratio (220, 340 & 470 mm2 ml−1) of the RCM to the gold nanoplate solution were varied during the synthesis process to determine the effect of each parameter on gold nanoplates yield, LSPR peak placement and stability. Results indicate the ability of the RCM to remove ∼99% of the contaminant small gold colloid (<10 nm) produced during the synthesis process, while producing a 72% higher yield of gold nanoplates compared to a conventional one-step fabrication process. Increasing the MWCO of the RCM from 3.5 kDa to 15 kDa was found to blue shift the LSPR peak down by 40 nm. Increasing the SA/Vol ratio and temperature blue shifted the LSPR peak wavelength by hundreds of nanometers with the nIR absorbing gold nanoplate LSPR peak occurring within the range of 650–1100 nm. It was also discovered that the gold nanoplates fabricated via the DiaSynth process with dialysis (Process 1) displayed an increase in stability over time without the need of a capping agent. With the increased gold nanoplate stability, further purification and isolation of gold nanoplates was possible through sedimentation over time. This study demonstrated that increasing the temperature, SA/Vol, and MWCO of the RCM allows production of gold nanoplates of increased purity compared to other methods and the ability to tailor the tunability of the LSPR peak to a desired wavelength.