Biotemplating Plasmonic Nanoparticles Using Intact Microfluidic Vasculature of Leaves

Leaves are an abundant natural resource, and consist of a sophisticated microfluidic network of veins that transport nutrients and water, thereby enabling photosynthesis. Here, we simultaneously exploit the microfluidics as well as chemistry of processed leaf vasculature (venation) in order to template the in situ generation of plasmonic metal (gold and silver) nanoparticles under ambient conditions. This biotemplating approach involves capillary flow of metal salts through skeleton leaf vasculature, and does not require additional reducing agents for plasmonic nanoparticle formation. Gold nanoparticles, 30–40 nm in diameter, and silver nanoparticles, approximately 9 nm in diameter, were formed within the intact leaf vasculature using this method. Absorption spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and electron diffraction analyses were employed to ascertain the formation of nanoparticles in the leaf veins. Fourier transform infrared (FT-IR) spectroscopy was employed in order to obtain insights into functional groups responsible for formation of the plasmonic nanoparticles within the leaves. Gold nanoparticles, templated within leaves, demonstrated excellent catalytic properties, thereby imparting catalytic and plasmonic properties to the leaf itself. Furthermore, nanoparticles can be recovered from the leaves as soluble dispersions by simply combusting the organic leaf matter. Taken together, this is a simple yet powerful biotemplating approach for the generation of plasmonic nanoparticles and formation of biotic–abiotic structures for diverse, low-cost applications in sensing, catalysis, and medicine

Investigation of Phase Separation Behavior and Formation of Plasmonic Nanocomposites from Polypeptide-Gold Nanorod Nanoassemblies

Genetically engineered elastin-like polypeptides (ELP) can be interfaced with cetyltrimethyl ammonium bromide (CTAB)-stabilized gold nanorods (GNRs) resulting in the formation of stable dispersions (nanoassemblies). Increasing the dispersion temperature beyond the ELP transition temperature results in phase separation and formation of solid-phase ELP-GNR matrices (nanocomposites). Here, we investigated different physicochemical conditions that influence nanocomposite formation from temperature-induced phase separation of ELP-GNR nanoassemblies. The presence of cetyltrimethyl ammonium bromide (CTAB), used to template the formation of gold nanorods, plays a significant role in the phase separation behavior, with high concentrations of the surfactant leading to dramatic enhancements in ELP transition temperature. Nanocomposites could be generated at 37 °C in the presence of low CTAB concentrations (<1.5 mM); higher concentrations of CTAB necessitated higher temperatures (60 °C) due to elevated transition temperatures. The concentration of gold nanorods, however, had minimal influence on the phase separation behavior and nanocomposite formation. Further analysis of the kinetics of nanocomposite formation using a mathematical model indicated that CTAB largely influenced the early event of coacervation of ELP-GNR nanoassemblies leading to nanocomposites, but had minimal effect on nanocomposite maturation, which is a later-stage longer event. Finally, nanocomposites prepared in the presence of low CTAB concentrations demonstrated a superior photothermal response following laser irradiation compared to those generated using higher CTAB concentrations. Our results on understanding the formation of plasmonic/photothermal ELP-GNR nanocomposites have significant implications for tissue engineering, regenerative medicine, and drug delivery

Parallel Synthesis of Poly(amino ether)-Templated Plasmonic Nanoparticles for Transgene Delivery

Plasmonic nanoparticles have been increasingly investigated for numerous applications in medicine, sensing, and catalysis. In particular, gold nanoparticles have been investigated for separations, sensing, drug/nucleic acid delivery, and bioimaging. In addition, silver nanoparticles demonstrate antibacterial activity, resulting in potential application in treatments against microbial infections, burns, diabetic skin ulcers, and medical devices. Here, we describe the facile, parallel synthesis of both gold and silver nanoparticles using a small set of poly­(amino ethers), or PAEs, derived from linear polyamines, under ambient conditions and in absence of additional reagents. The kinetics of nanoparticle formation were dependent on PAE concentration and chemical composition. In addition, yields were significantly greater in case of PAEs when compared to 25 kDa poly­(ethylene imine), which was used as a standard catonic polymer. Ultraviolet radiation enhanced the kinetics and the yield of both gold and silver nanoparticles, likely by means of a coreduction effect. PAE-templated gold nanoparticles demonstrated the ability to deliver plasmid DNA, resulting in transgene expression, in 22Rv1 human prostate cancer and MB49 murine bladder cancer cell lines. Taken together, our results indicate that chemically diverse poly­(amino ethers) can be employed for rapidly templating the formation of metal nanoparticles under ambient conditions. The simplicity of synthesis and chemical diversity make PAE-templated nanoparticles useful tools for several applications in biotechnology, including nucleic acid delivery

Gold Nanorod-Collagen Nanocomposites as Photothermal Nanosolders for Laser Welding of Ruptured Porcine Intestines

Surgical site infection and postoperative leakage are complications that may develop following colorectal surgery and result in fatal consequences. Rapid, fluid-tight wound closure through laser tissue welding (LTW) can reduce postoperative leakage and thus decrease infection. Laser tissue welding involves generation of localized heat by exposing an exogenous chromophore to near-infrared (NIR) irradiation in order to seal wounds. In this study, we generated gold nanorod (GNR)-collagen nanocomposites (NCs) for laser-facilitated welding of ruptured intestinal tissue. The fluid content, stiffness, elasticity, and laser-induced temperature response of these nanocomposites were modulated to optimize laser-induced tissue fusion and minimize tissue damage. In addition, the effect of laser operating parameters including power density, femtosecond pulsed wave (PW) or continuous wave (CW) laser, and exposure duration were all studied. Laser power density and treatment duration significantly affected the temperatures reached during welding, as well as tissue weld strength and burst pressure. CW laser was found to induce significantly higher temperatures of the nanocomposites during treatment than PW laser, but the differences in weld strength and burst pressure for the two laser types were insignificant. This suggests that PW lasers can result in robust welds while minimizing potential thermal damage compared to CW lasers. The ultimate tensile strength of welded ruptured tissue was returned to as high as 68% of the native tissue strength through laser treatment, and laser treatment with these nanocomposites restored up to 64% of native tissue leak pressure and 42% of burst pressure. To the best of our knowledge, the laser power densities used (≤2.50 W/cm²) are among the lowest reported for laser tissue welding, and the laser configuration and use require very little surgical skill. Our results indicate that GNR-collagen nanocomposites are promising photothermal biomaterials in laser tissue welding applications

Laser Welding of Ruptured Intestinal Tissue Using Plasmonic Polypeptide Nanocomposite Solders

Approximately 1.5 million people suffer from colorectal cancer and inflammatory bowel disease in the United States. Occurrence of leakage following standard surgical anastomosis in intestinal and colorectal surgery is common and can cause infection leading to life-threatening consequences. In this report, we demonstrate that plasmonic nanocomposites, generated from elastin-like polypeptides (ELPs) cross-linked with gold nanorods, can be used to weld ruptured intestinal tissue upon exposure to near-infrared (NIR) laser irradiation. Mechanical properties of these nanocomposites can be modulated based on the concentration of gold nanorods embedded within the ELP matrix. We employed photostable, NIR-absorbing cellularized and noncellularized GNR–ELP nanocomposites for <i>ex vivo</i> laser welding of ruptured porcine small intestines. Laser welding using the nanocomposites significantly enhanced the tensile strength, leakage pressure, and bursting pressure of ruptured intestinal tissue. This, in turn, provided a liquid-tight seal against leakage of luminal liquid from the intestine and resulting bacterial infection. This study demonstrates the utility of laser tissue welding using plasmonic polypeptide nanocomposites and indicates the translational potential of these materials in intestinal and colorectal repair

A Colorimetric Plasmonic Nanosensor for Dosimetry of Therapeutic Levels of Ionizing Radiation

Modern radiation therapy using highly automated linear accelerators is a complex process that maximizes doses to tumors and minimizes incident dose to normal tissues. Dosimeters can help determine the radiation dose delivered to target diseased tissue while minimizing damage to surrounding healthy tissue. However, existing dosimeters can be complex to fabricate, expensive, and cumbersome to operate. Here, we demonstrate studies of a liquid phase, visually evaluated plasmonic nanosensor that detects radiation doses commonly employed in fractionated radiotherapy (1–10 Gy) for tumor ablation. We accomplished this by employing ionizing radiation, in concert with templating lipid surfactant micelles, in order to convert colorless salt solutions of univalent gold ions (Au¹) to maroon-colored dispersions of plasmonic gold nanoparticles. Differences in color intensities of nanoparticle dispersions were employed as quantitative indicators of the radiation dose. The nanoparticles thus formed were characterized using UV–vis absorbance spectroscopy, dynamic light scattering, and transmission electron microscopy. The role of lipid surfactants on nanoparticle formation was investigated by varying the chain lengths while maintaining the same headgroup and counterion; the effect of surfactant concentration on detection efficacy was also investigated. The plasmonic nanosensor was able to detect doses as low as 0.5 Gy and demonstrated a linear detection range of 0.5–2 Gy or 5–37 Gy depending on the concentration of the lipid surfactant employed. The plasmonic nanosensor was also able to detect radiation levels in anthropomorphic prostate phantoms when administered together with endorectal balloons, indicating its potential utility as a dosimeter in fractionated radiotherapy for prostate cancer. Taken together, our results indicate that this simple visible nanosensor has strong potential to be used as a dosimeter for validating delivered radiation doses in fractionated radiotherapies in a variety of clinical settings

Parallel Synthesis and Quantitative Structure–Activity Relationship (QSAR) Modeling of Aminoglycoside-Derived Lipopolymers for Transgene Expression

We describe the parallel synthesis of lipopolymers generated by conjugating alkanoyl chlorides to polymers derived from aminoglycoside antibiotic monomers as novel vehicles for transgene delivery and expression in mammalian cells. Parallel screening of lipopolymers led to the identification of six leads that demonstrated higher transgene expression efficacies in several cancer cells, when compared to the parental polymers as well as 25 kDa poly­(ethylene imine), a current standard for polymer-mediated transgene expression. Quantitiative structure–activity relationship (QSAR)-based cheminformatics modeling was employed in order to investigate the role of lipopolymer physicochemical properties (molecular descriptors) on transgene expression efficacy. The predictive ability of the QSAR model, investgated using lipopolymers not employed for training the model, demonstrated excellent agreement with experimentally observed transgene expression. Our findings indicate that lipid substitution on aminoglycoside-derived polymers results in high levels of transgene expression compared to unsubstituted polymers. Taken together, these materials show significant promise in nonviral transgene delivery with several applications in biotechnology and medicine

Hydrogel Nanosensors for Colorimetric Detection and Dosimetry in Proton Beam Radiotherapy

Proton beam therapy (PBT) is a state-of-the-art radiotherapy treatment approach that uses focused proton beams for tumor ablation. A key advantage of this approach over conventional photon radiotherapy (XRT) is the unique dose deposition characteristic of protons, which results in superior healthy tissue sparing. This results in fewer unwanted side effects and improved outcomes for patients. Currently available dosimeters are intrinsic, complex, and expensive and are not routinely used to determine the dose delivered to the tumor. Here, we report a hydrogel-based plasmonic nanosensor for detecting clinical doses used in conventional and hyperfractionated proton beam radiotherapy. In this nanosensor, gold ions, encapsulated in a hydrogel, are reduced to gold nanoparticles following irradiation with proton beams. Formation of gold nanoparticles renders a color change to the originally colorless hydrogel. The intensity of the color can be used to calibrate the hydrogel nanosensor in order to quantify different radiation doses employed during proton treatment. The potential of this nanosensor for clinical translation was demonstrated using an anthropomorphic phantom mimicking a clinical radiotherapy session. The simplicity of fabrication, detection range in the fractionated radiotherapy regime, and ease of detection with translational potential makes this a first-in-kind plasmonic colorimetric nanosensor for applications in clinical proton beam therapy

Aminoglycoside Antibiotic-Derived Anion-Exchange Microbeads for Plasmid DNA Binding and in Situ DNA Capture

Plasmid DNA (pDNA) therapeutics are being investigated for gene therapy and DNA vaccines against diseases including cancer, cystic fibrosis and AIDS. In addition, several applications in modern biotechnology require pDNA for transient protein production. Here, we describe the synthesis, characterization, and evaluation of microbeads (“Amikabeads”) derived from the aminoglycoside antibiotic amikacin for pDNA binding and in situ DNA capture from mammalian cells. The parental aminoglycoside-derived microbeads (Amikabeads-P) acted as anion-exchange materials, and demonstrated high capacities for binding pDNA. Binding of pDNA was significantly enhanced following quaternization of the amines on the microbeads (Amikabeads-Q). Amikabeads were further employed for the disruption and extraction of DNA from mammalian cells, indicating their utility for in situ DNA capture. Our results indicate that Amikabeads are a novel material, with multiple reactive groups for further conjugation, and can have several applications in plasmid DNA biotechnology

Investigation into Pseudo-Capacitance Behavior of Glycoside-Containing Hydrogels

Electrochemical pseudocapacitors are an attractive choice for energy storage applications because they offer higher energy densities than electrostatic or electric double layer capacitors. They also offer higher power densities in shorter durations of time, as compared to batteries. Recent efforts on pseudocapacitors include biocompatible hydrogel electrolytes and transition metal electrodes for implantable energy storage applications. Pseudocapacitive behavior in these devices has been attributed to the redox reactions that occur within the electric double layer, which is formed at the electrode–electrolyte interface. In the present study, we describe a detailed investigation on redox reactions responsible for pseudocapacitive behavior in glycoside-containing hydrogel formulations. Pseudocapacitive behavior was compared among various combinations of biocompatible hydrogel electrolytes, using carbon tape electrodes and transition metal electrodes based on fluorine-doped tin oxide. The hydrogels demonstrated a pseudocapacitive response only in the presence of transition metal electrodes but not in the presence of carbon electrodes. Hydrogels containing amine moieties showed greater energy storage than gels based purely on hydroxyl functional groups. Furthermore, energy storage increased with greater amine content in these hydrogels. We claim that the redox reactions in hydrogels are largely based on Lewis acid–base interactions, facilitated by amine and hydroxyl side groups along the electrolyte chain backbones, as well as hydroxylation of electrode surfaces. Water plays an important role in these reactions, not only in terms of providing ionic radicals but also in assisting ion transport. This understanding of redox reactions will help determine the choice of transition metal electrodes, Lewis acid–base pairs in electrolytes, and medium for ionic transport in future biocompatible pseudocapacitors