Liyuan Ma

Superhydrophobic Membranes with Ordered Arrays of Nanospiked Microchannels for Water Desalination

Membrane distillation can desalinate seawater using low-grade heat energy or solar heat, but it has limited mass fluxes and membrane fouling issues. Glass membranes with integrated arrays of nanospiked microchannels and a narrow pore size distribution are made through a process that involves glass fiber drawing, dissolving template material from microchannels and differential chemical etching. After surface modification, superhydrophobic glass membranes with water contact angles of over 160 degrees are produced because of the formations of ordered arrays of spiked nanostructures. The superhydrophobic membrane has shown better antifouling ability and higher flux than those of existing polymer membranes, especially at high salt concentration, owing to its large pore diameter, straight pore shape, narrow pore size distribution, high chemical and thermal stabilities, and water-repelling ability.

Three-Dimensional Microtissue Assay for High-Throughput Cytotoxicity of Nanoparticles

Traditional in vitro nanotoxicity researches are conducted on cultured two-dimensional (2D) monolayer cells and thereby cannot reflect organism response to nanoparticle toxicities at tissue levels. This paper describes a new, high-throughput approach to test in vitro nanotoxicity in three-dimensional (3D) microtissue array, where microtissues are formed by seeding cells in nonsticky microwells, and cells are allowed to aggregate and grow into microtissues with defined size and shape. Nanoparticles attach and diffuse into microtissues gradually, causing radial cytotoxicity among cells, with more cells being killed on the outer layers of the microtissue than inside. Three classical toxicity assays [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] (MTT), glucose-6-phosphate dehydrogenase (G6DP), and calcein AM and ethidium homodimer (calcein AM/EthD-1)] have been adopted to verify the feasibility of the proposed approach. Results show that the nanotoxicities derived from this method are significantly lower than that from traditional 2D cultured monolayer cells (p < 0.05). Equipped with a microplate reader or a microscope, the nanotoxicity assay could be completed automatically without transferring the microtissue, ensuring the reliability of toxicity assay. The proposed approach provides a new strategy for high-throughput, simple, and accurate evaluation of nanoparticle toxicities by combining 3D microtissue array with a panel of classical toxicity assays.

Single Cell Array Based Assay for in Vitro Genotoxicity Study of Nanomaterials

This paper describes the use of a single cell array based assay for genotoxicity study of nanomaterials using normal human fetal fibroblast cells obtained from two-dimensional (2D) monolayer cultures and three-dimensional (3D) microtissue. After being exposed to a suspension of nanomaterials, cells are attached onto microfabricated patches with proper modification through electrostatic attraction and embedded in hydrogel. The damaged DNAs diffuse in gel matrix and form observable halo structures, where the level of DNA damage is quantified from the dimensions of core and halo. A concentration dependent genotoxicity has been found in nanomaterials. Compared to the traditional cytotoxicity (live/dead) assay, the genotoxicity results from the single cell array based assay are more robust and sensitive at the same exposure concentration, indicating that nanomaterials cause significant DNA damage without detectable cytotoxicity. In addition, cells from 3D microtissues are less damaged than 2D culture due to different cell microenvironments.

Highly sensitive thermal detection of thrombin using aptamer-functionalized phase change nanoparticles

This paper describes a novel thermal biosensing technique for the highly sensitive and selective detection of thrombin using RNA aptamer-functionalized phase change nanoparticles as thermal probes. The presence of thrombin in solution leads to attachment of nanoparticles onto a substrate modified with the same aptamer by forming sandwiched complexes. The phase changes of nanoparticles from solid to liquid adsorb heat energy and generate sharp melting peaks during linear temperature scans, where the positions and areas of the melting peaks reflect the presence and the amount of thrombin, respectively. A detection sensitivity of 22 nM is achieved on flat aluminum surfaces, and the sensitivity can be enhanced by four times using silicon nanopillar substrates that have higher surface area. The thermal detection is immune to colored species in solution and has been used directly to detect thrombin in serum samples. By combining the high specificity of aptamers and the large surface area of silicon nanostructures, the thermal signals obtained during phase change of nanoparticles provide a highly sensitive, selective and low-cost method for thrombin detection.

Multiplexed highly sensitive detections of cancer biomarkers in thermal space using encapsulated phase change nanoparticles

We describe a multiplexed highly sensitive method to detect cancer biomarkers using silica encapsulated phase change nanoparticles as thermal barcodes. During phase changes, nanoparticles absorb heat energy without much temperature rise and show sharp melting peaks (0.6 °C). A series of phase change nanoparticles of metals or alloys can be synthesized in such a way that they melt between 100 and 700 °C, thus the multiplicity could reach 1000. The method has high sensitivity (8 nM) that can be enhanced using materials with large latent heat, nanoparticles with large diameter, or reducing the grafting density of biomolecules on nanoparticles.

Cationic surface modification of gold nanoparticles for enhanced cellular uptake and X-ray radiation therapy.

A challenge of X-ray radiation therapy is that high dose X-ray can damage normal cells and cause side effects. This paper describes a new nanoparticle-based method to reduce X-ray dose in radiation therapy by internalization of gold nanoparticles that are modified with cationic molecules into cancer cells. A cationic thiol molecule is synthesized and used to modify gold nanoparticles in a one-step reaction. The modified nanoparticles can penetrate cell membranes at high yield. By bring radio-sensitizing gold nanoparticles closer to nuclei where DNA is stored, the total X-ray dose needed to kill cancer cells has been reduced. The simulation of X-ray-gold nanoparticle interaction also indicates that Auger electrons contribute more than photoelectrons.

Mechanical and Morphological Analysis of Cancer Cells on Nanostructured Substrates.

Cancer metastasis is a major cause of cancer-induced deaths in patients. Mimicking nanostructures of an extracellular matrix surrounding cancer cells can provide useful clues for metastasis. This paper compares the morphology, proliferation, spreading, and stiffness of highly aggressive glioblastoma multiforme cancer cells and normal fibroblast cells seeded on a variety of ordered polymeric nanostructures (nanopillars and nanochannels). Both cell lines survive and proliferate on the nanostructured surface and show more similarity on nanostructured surfaces than on flat surfaces. Although both show similar stiffness on the nanochannel surface, glioblastomas are softer, spread to a larger area, and elongate less than fibroblasts. The nanostructured surfaces are useful for in vitro model of an extracellular matrix to study the cancer cell migratory phenotype.

3D ordered assemblies of semiconductive micro/nanowires using microscale fibrous building blocks.

Three-dimensional (3D) ordered assemblies of semiconductive micro/nanowires are made by match-stick assembly of fibrous building blocks (FBBs). A glass tube filled with powders of starting material is processed drawn into centimeter-long, micrometer-diameter FBBs with controlled diameter and spacing. By repeating a draw-cut-stack process, the diameter and spacing of filling material can be programmably reduced from millimeters to hundreds of nanometers. The FBBs are densely packed into 3D ordered structures such that wires in one layer are at defined angle (theta) relative to those in the adjacent layers, where theta is between 0 and 180 degrees. The electrical measurements at bundled wires and single wire level confirm semiconducting behavior of wires. By directly manipulating microscale FBBs, the method allows high yield production of 3D ordered micro/nanowires with controlled position and orientation, enabling the construction of a new class of micro/nanomaterials.

Curved Microwell Arrays Created by Diffusion-Limited Chemical Etching of Artificially Engineered Solids

A new method based on diffusion-limited chemical etching has been developed for the productions of ordered arrays of curved microwells. Fiber-drawing nanomanufacturing is used to make ordered glass composites with controlled structure and composition. The differential chemical etching of two glasses in the composite preferentially etches one glass material away and generates ordered microwell arrays. The microwells can be replicated onto polymer films to form microdome arrays. Monte Carlo simulation illustrates the diffusion-controlled etching process. The etched microwells have been used to prepare micro/nanocrystals of proteins and inorganic materials with controlled sizes.

Electrically Modulated Localized Surface Plasmon around Self-Assembled-Monolayer-Covered Nanoparticles

This article reports the observation of electrical modulation of localized surface plasmon around self-assembled monolayer (SAM)-modified gold nanoparticles and the establishment of a new spectroscopy technique, that is, dynamic electro-optical spectroscopy (DEOS). The gold nanoparticles are deposited onto a transparent conductive substrate, and an electrical bias applied on the conductive substrate can cause shift of resonance plasmon response, where the direction of peak shift is related to the polarity of applied bias. The peak shift observed at 2.4 V is approximately ten times larger than those reported in previous work. It is postulated that significant peak shift is the result of reorientation of adsorbed water on electrode, which can change local dielectric environment of nanoparticles. An energy barrier is identified when adsorbed water molecules are turned from oxygen-down to oxygen-up. Frequency-dependent peak shifts on surface-modified gold nanoparticles show that reorientation is a fast reversible process with rich dynamics.