Fate and budget of poly- and perfluoroalkyl substances in three common garden plants after experimental additions with contaminated river water.

Poly- and perfluoroalkyl substances (PFAS) have become ubiquitous contaminants in the environment. Contamination of the terrestrial ecosystem can occur from the release of aqueous film forming foams (AFFF) used in firefighting operations. Following soil contamination with AFFF, studies report root uptake and translocation of PFAS to other plant organs, typically favouring the short chain moiety. This body of experimental work often focuses on edible organs and generally lacks entire PFAS budgets. Here, we calculate short chain (≤6 carbons) and long chain (≥6 or ≥ 7 carbons) PFAS concentrations and respective budgets for terrestrial multimedia mesocosms (plants, soil and lysimeter) of three common agricultural plants (tomato, lettuce and beet) following irrigation with low level PFAS (<1 µg L-1) contaminated river water (short chain: 167 ng L-1; long chain 526 ng L-1). Total net recoveries were strong, ranging between 91% and 118% of added PFAS across all media. While soil was the largest receptor of PFAS in general (∼70% and 115%), there was considerable mobility to various media, including vegetation (∼3% and 20%) and leachate (∼1%). Translocation of short chain PFAS to tomato flowers resulted with biomagnified concentrations (maximus >4000 ng g-1) and accounted for 1.4% of PFAS additions. While smaller tomato fruits had higher concentrations of short chain PFAS, larger fruit had more total PFAS mass. This work provides a detailed description of the fate of short and long chain PFAS when added to relatively uncontaminated terrestrial agricultural systems. We show low-level PFAS concentrations from real-world irrigation sources can affect various receptors across the multimedia landscape. This is most evident in tomato flowers and fruit where biomagnification and high total masses of short chain PFAS occurred which could have implications for pollinators and consumption, respectively.

Self-reference and random sampling approach for label-free identification of DNA composition using plasmonic nanomaterials.

The analysis of DNA has led to revolutionary advancements in the fields of medical diagnostics, genomics, prenatal screening, and forensic science, with the global DNA testing market expected to reach revenues of USD 10.04 billion per year by 2020. However, the current methods for DNA analysis remain dependent on the necessity for fluorophores or conjugated proteins, leading to high costs associated with consumable materials and manual labor. Here, we demonstrate a potential label-free DNA composition detection method using surface-enhanced Raman spectroscopy (SERS) in which we identify the composition of cytosine and adenine within single strands of DNA. This approach depends on the fact that there is one phosphate backbone per nucleotide, which we use as a reference to compensate for systematic measurement variations. We utilize plasmonic nanomaterials with random Raman sampling to perform label-free detection of the nucleotide composition within DNA strands, generating a calibration curve from standard samples of DNA and demonstrating the capability of resolving the nucleotide composition. The work represents an innovative way for detection of the DNA composition within DNA strands without the necessity of attached labels, offering a highly sensitive and reproducible method that factors in random sampling to minimize error.

Simulated Raman correlation spectroscopy for quantifying nucleic acid-silver composites.

Plasmonic devices are of great interest due to their ability to confine light to the nanoscale level and dramatically increase the intensity of the electromagnetic field, functioning as high performance platforms for Raman signal enhancement. While Raman spectroscopy has been proposed as a tool to identify the preferential binding sites and adsorption configurations of molecules to nanoparticles, the results have been limited by the assumption that a single binding site is responsible for molecular adsorption. Here, we develop the simulated Raman correlation spectroscopy (SRCS) process to determine which binding sites of a molecule preferentially bind to a plasmonic material and in what capacity. We apply the method to the case of nucleic acids binding to silver, discovering that multiple atoms are responsible for adsorption kinetics. This method can be applied to future systems, such as to study the molecular orientation of adsorbates to films or protein conformation upon adsorption.

Maximizing the electromagnetic and chemical resonances of surface-enhanced Raman scattering for nucleic acids.

Although surface-enhanced Raman spectroscopy (SERS) has previously been performed with nucleic acids, the measured intensities for each nucleic acid have varied significantly depending on the SERS substrate and excitation wavelength. We have demonstrated that the charge-transfer (CT) mechanism, also known as the chemical enhancement of SERS, is responsible for the discrepancies previously reported in literature. The electronic states of cytosine and guanine attached to silver atoms are computationally calculated and experimentally measured to be in the visible range, which leads to a resonance Raman effect at the corresponding maximum wavelengths. The resulting SERS measurements are in good agreement with the simulated values, in which cytosine-silver shows stronger enhancement at 532 nm and guanine-silver shows stronger enhancement at 785 nm. An atomic layer of aluminum oxide is deposited on substrates to prevent charge-transfer, and corresponding measurements show weaker Raman signals caused by the suppression of the chemical resonance. These findings suggest the optimal SERS signal can be achieved by tuning the excitation wavelength to match both the electromagnetic and chemical resonances, paving the way for future single molecule detection of nucleic acids other than adenine.

Optofluidic devices and applications in photonics, sensing and imaging.

Optofluidics integrates the fields of photonics and microfluidics, providing new freedom to both fields and permitting the realization of optical and fluidic property manipulations at the chip scale. Optofluidics was formed only after many breakthroughs in microfluidics, as understanding of fluid behaviour at the micron level enabled researchers to combine the advantages of optics and fluids. This review describes the progress of optofluidics from a photonics perspective, highlighting various optofluidic aspects ranging from the device's property manipulation to an interactive integration between optics and fluids. First, we describe photonic elements based on the functionalities that enable fluid manipulation. We then discuss the applications of optofluidic biodetection with an emphasis on nanosensing. Next, we discuss the progress of optofluidic lenses with an emphasis on its various architectures, and finally we conceptualize on where the field may lead.

Excitation of Cy5 in self-assembled lipid bilayers using optical microresonators.

Due to their sensitivity and temporal response, optical microresonators are used extensively in the biosensor arena, particularly in the development of label-free diagnostics and measurement of protein kinetics. In the present letter, we investigate using microcavities to probe molecules within biomimetic membranes. Specifically, a method for self-assembling lipid bilayers on spherical microresonators is developed and the bilayer-nature is verified. Subsequently, the microcavity is used to excite a Cy5-conjugated lipid located within the bilayer while the optical performance of the microcavity is characterized. The emission wavelength of the dye and the optical behavior of the microcavity agree with theoretical predictions.