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

HYPOTHESIS: A 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. EXPERIMENTS: Chloroauric 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. FINDINGS: The 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.

Enhanced penetration into 3D cell culture using two and three layered gold nanoparticles.

Nano-scale particles sized 10-400 nm administered systemically preferentially extravasate from tumor vasculature due to the enhanced permeability and retention effect. Therapeutic success remains elusive, however, because of inhomogeneous particle distribution within tumor tissue. Insufficient tumor vascularization limits particle transport and also results in avascular hypoxic regions with non-proliferating cells, which can regenerate tissue after nanoparticle-delivered cytotoxicity or thermal ablation. Nanoparticle surface modifications provide for increasing tumor targeting and uptake while decreasing immunogenicity and toxicity. Herein, we created novel two layer gold-nanoshell particles coated with alkanethiol and phosphatidylcholine, and three layer nanoshells additionally coated with high-density-lipoprotein. We hypothesize that these particles have enhanced penetration into 3-dimensional cell cultures modeling avascular tissue when compared to standard poly(ethylene glycol) (PEG)-coated nanoshells. Particle uptake and distribution in liver, lung, and pancreatic tumor cell cultures were evaluated using silver-enhancement staining and hyperspectral imaging with dark field microscopy. Two layer nanoshells exhibited significantly higher uptake compared to PEGylated nanoshells. This multilayer formulation may help overcome transport barriers presented by tumor vasculature, and could be further investigated in vivo as a platform for targeted cancer therapies.

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

Gold 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. FROM THE CLINICAL EDITOR: PEGylated 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 shape and size, 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 540 J (3 W cm(-2) for 3 min) 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.