Dhruvinkumar Patel

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.

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.

Gold Nanoplates as Cancer-Targeted Photothermal Actuators for Drug Delivery and Triggered Release

The selective exposure of cancerous tissue to systemically delivered chemotherapeutic agents remains a major challenge facing cancer therapy. To address this question, a near infrared responsive oligonucleotide-coated AS1411, hairpin, or both gold nanoplate loaded with doxorubicin is demonstrated to be nontoxic to cells without triggered release, while being acutely toxic to cells after 5 minutes of laser exposure to trigger DOX release. Conjugation of oligonucleotides to the nanoplates is confirmed by an average increase in hydrodynamic diameter of 30.6 nm, an average blue shift of the plasmon resonance peak by 36 nm, and an average −10 mV shift in zeta potential of the particles. DOX loading through intercalation into the hairpin DNA structure is confirmed through fluorescence measurements. For both GNP-Hairpin and GNP-Hairpin-AS1411, ~60% of loaded DOX is released after the first 5 minutes of laser exposure λ=817 nm, with complete release after two more 5-minute exposures. Preliminary proof of concept is demonstrated in vitro using A549 and MDA-MB-231 cell lines as models for breast and lung cancer, respectively. Exposure of cells to untriggered DOX-loaded conjugate with no laser exposure results in little to no toxicity, while laser-triggered release of DOX causes significant cell death.

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.

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.