Exploring the cell-material interface is an emerging area of great interest in biomaterial science. Specifically, creating nanostructured surface interfaces to improve biomaterial efficacy is one of these key focus topics. As an example, an increasing number of studies have demonstrated the positive role nanostructured surfaces can have towards promoting various cell functions. However, the relevant mechanism behind this improvement in biological interactions at the cell-implant interface is not well understood. For this reason, here, osteoblast (bone forming cells) and fibroblast (fibrous, soft tissue forming cells) functions (including adhesion and proliferation) on two carefully fabricated diamond films with dramatically different topographies were tested. The results revealed greater cell responses on nanocrystalline diamond (grain sizes <100nm) compared to submicron crystalline diamond (grain sizes 200˜1000nm). In order to understand this positive impact of diamond nanotopography on cell responses, fibronectin absorption and subsequent cell spreading were studied. More importantly, cell filopodia extensions were also studied through computational mechanical modeling. A deflection-diffusion model of cell filopodia extension was established and clearly suggested that increasing the lateral dimension or height of nanometer surface features could inhibit cell filopodia extension and decrease cell spreading. Both the experiments and modeling from this study indicated that a nanometer surface topography can enhance cell responses to promote implant efficacy.

Bioactive glass is known for its potential as a bone scaffold due to its ability to stimulate osteogenesis and differentiation of stem cells into bone cells. In an attempt to investigate if we can increase these potentials, we decorated the structure of the bioactive glass made by the sol-gel technique with 3 peptides sequences from different proteins known for their potentials to stimulate the osteogensis process (fibronectin, BMP-2 and protein kinase CKI). This material was tested with Human Mesenchymal Stem Cells (hMSCs) and MC-3T3 preosteoblasts to see the difference in the effect on uncommitted and committed cells. The bioactive glass sol with and without the peptides was dip coated onto glass cover slips, leading to a film of the material, surface decorated with the peptides of choice. The two cell types were seeded onto the materials in standard proliferation medium without additives for differentiation induction. Cells were also grown on tissue culture treated cover slips with and without differentiation induction media as positive and negative controls, respectively. The cells were grown on the materials for a total of five weeks, and were tested at four time points (weekly from week two) by immunocytochemical assays to investigate the levels of different osteogenic markers (osteopontin, osteocalcin and osteonectin) and by qRT-PCR to investigate the mRNA potential of the same proteins. On the native bioactive glass samples, the hMSCs and the MC-3T3s adhered poorly. On peptide-decorated samples, the hMSC adhered poorly, however, the MC-3T3 cells appear to differentiate at a rate that is equal to or faster than the positive control, indicating that the peptide effect is similar to that achieved by traditional BMP-2 soluble protein techniques. This supports our hypothesis that adding specific peptide sequences known for their effects in cells adhesion, proliferation and differentiation can increase the potential of the bioactive glass as a scaffold for bone tissue engineering. The data, however, leads to some questions regarding the MC-3T3 cell model for use in further studies.

We report on the phenomenology and kinetics of a self-spreading supported lipid bilayer (SLB) on a patterned surface. Analyses of our experiments provided two findings. One is that the self-spreading velocity increased when the SLB reached the inlet of the line patterns. This capillary effect-like behavior indicates an additional attractive interaction for SLB spreading in the line patterns. The other is that the front edge is always normal to the spreading direction even for curving lines. This can be attributed to the line tension at the spreading front edge.

Functional carbonaceous materials, organic electronic materials, and polymer materials which "speak the language" of biomaterials in their propensity for hierarchical structure formation play a central role in current materials science research. In this context, we prepared hierarchically structured conjugated polymers from diacetylene macromonomers based on β-sheet-forming oligopeptide-polymer conjugates as supramolecular building blocks. The monomers gave rise to supramolecular polymers with a finite number of strands, a uniform diameter of a few nanometers, and defined superstructures. These were then converted into conjugated polymers under retention of their hierarchical structures, leading to poly(diacetylene)s with multiple-helical quaternary structures and a rich folding behavior. The diacetylene macromonomers served as a model system to improve our understanding of how to use hydrogen-bonding sites in order to control the placement of reactive molecular precursors for hierarchically structured organic materials.

CA-125 and carcinoembryonic antigen (CEA) are two biomarkers present in blood that can indicate the presence of ovarian cancer. They can also be used, both in conjunction with each other and independently, to determine the effectiveness of the treatment being meted for the disease. A label-free multiplexed interdigitated electrode array (IDEA) immunosensor was developed to detect both CA-125 and CEA in buffer solution at levels typically seen in patients with ovarian cancer . Electrochemical impedance spectroscopy was used to measure the increase in impedance when a binding event occurred between the target antigen and its specific antibody that was anchored to the surface of an interdigitated electrode array. CA-125 was detected in concentrations as low as 10units/mL and as high as 80units/mL. CEA was detected in concentrations as low as 1pg/mL and as high as 10μg/mL.

A significant challenge for high throughput nucleic acid analysis and sequencing is to increase both throughput and sensitivity. Electrical detection methods are advantageous since they can be easily scaled to high density arrays, are highly sensitive, and do not require bulky optical equipment for readout. A focus of most nucleic acid based sensors is the detection of sequence-specific hybridization events between complementary strands of DNA or RNA. These hybridization events can be detected electrically, due to the intrinsic negative charge associated with the phosphate-rich nucleic acid backbone. Field effect transistors (FETs) and high electron mobility transistors (HEMTs) are ideal devices for detecting such hybridization events, due to their high sensitivity to changes in electrical field strength. A key concern for the construction of DNA-based FET and HEMT biosensors is the immobilization of probe oligonucleotides on the active region of the sensor. In previous work, our group has shown that single stranded DNA can be directly immobilized onto semiconductor materials without the need for complex surface chemistry or crosslinking strategies. In the present work, we have shown that the immobilization of single stranded DNA onto these materials is influenced by the terminal phosphate group of the DNA molecule, independent of backbone phosphates. This agrees with previous studies in which phosphates and phosphonates exhibited strong attachment to a variety of metal oxides. We have also shown that surface-immobilized DNA is available for hybridization and that hybridization is sequence specific. Phosphate-dependent immobilization was demonstrated for HfO2, AlGaN, and ZrO2 surfaces using optical detection of DNA-DNA hybridization, as well as x-ray photoelectron spectroscopy (XPS) analysis of DNA-modified surfaces.

The nanotechnology is undergoing enormous attention in the areas of biological research for clinical, environmental, and life sciences applications. One of the products from this new technology that attracts researcher’s attentions is the semiconductor quantum dot (QDs) nanoparticles, QDs possess incomparable advantages such as unique size-dependent physical properties, broad absorption spectrum, precise small bandwidth emission wavelength, as well as enhanced chemical and photochemical stability. The QDs can be modified for a controlled and enhanced endocytosis, enhanced cooperative binding activity, and easy introduction of multi-functionalities for medical applications such as targeted delivery and imaging. It can be used for complex studies that play very important roles in the modern biomedical researches. However, when performing the cell related assays, the non-specific cellular uptake of QDs is a major concern because they can lead to false positives or false results. In our study, we used different surface modified QDs treated with different blocking buffers to eliminate cellular uptake. The preliminary results showed that the cellular uptake of QDs can be eliminated by surface modification of the QD materials and by performing the assays in the presence of blocking buffers. As a result of the elimination of non-specific uptake of QDs the sensitivity and specificity of detection increased significantly.

Au-coated Pd (Au/Pd) nanocubes (˜250 nm in width) connected via a network of single-walled carbon nanotubes (SWCNTs) have been employed as an electrochemical biosensor. As previously reported, these in situ Au/Pd nanocube SWCNT networks are capable of ultrasensitive amperometric sensing of glucose, with a sensitivity, detection limit, and linear sensing range greater than similar CNT-based glucose biosensors. The 3D mass diffusion of glucose molecules to the Au/Pd nanocube surfaces, forced convection environment of the testing vial, and Brownian motion of the Au/Pd nanocubes are all likely factors contributing to the strong electrochemical performance of the Au/Pd-SWCNT biosensor. In an effort to elucidate the effects of these contributing factors, this work demonstrates an analytical biosensor capture kinetics model that analyzes the analyte-biosensor mass transfer by molecular diffusion and convection due to both the fluid motion within the test vial and the Brownian motion of the Au/Pd nanocubes themselves.

The biosensor capture kinetics model incorporates a quasi steady-state integrated incident flux equation to model mass diffusion of biomolecules to the surface of a 1D planar, 2D nanowire, and 3D nanosphere surface in Cartesian, cylindrical, and spherical coordinates respectively. A Burgers vortex model is introduced to analyze the biosensor diffusion boundary layer within a test vial that experiences fluid downwelling and upwelling within the vial center and boundaries due to the rotation of a magnetic stir bar. Finally the convection-diffusion equation simplified by Stokes flow is utilized to model the diffusion boundary layer of the Au/Pd nanocubes experiencing Brownian motion.

Several key conclusions can be interfered from this model. First, a biosensor experiencing 3D mass diffusion will exhibit a greater analyte concentration flux of at least one order of magnitude greater than a biosensor experiencing 2D diffusion and 1D mass diffusion in quiescent and convective fluid environments. Additionally, mass transfer by convection increases the concentration flux to the biosensor by inhibiting the continued advancement of the analyte depletion layer around the biosensor. Furthermore, the Brownian motion model of the Au/Pd nanocubes is shown to improve the mass transfer to the biosensor surface, portraying a substantial increase in amperometric current signal output as compared to a similar electrochemical-based biosensor with stationary Au/Pd nanocubes. In summary, the results of the biosensor capture kinetics model corroborate the high sensitivities and low detection limits previously observed experimentally by Au/Pd nanocube-SWCNT biosensors.

Brain machine interface (BMI) technology has been demonstrated to be a therapeutic solution for assisting people suffering from damage to the central nervous system (CNS), but BMI devices using implantable neural prosthetics have experienced difficulties in that they are recognized by glial cells as being foreign material, which leads to an immune response cascade process called gliosis. One material, cubic silicon carbide (3C-SiC), may provide an excellent solution for the generation of an implantable neural prosthetic interface component of a BMI system. We have recently reported on the biocompatibility of 3C-SiC with immortalized cells, and have extended this work by demonstrating neural cell action potential instigation via an electrode type device. Biocompatibility assessment of 3C-SiC was accomplished using in vitro methodology. 96 hour MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] assays were performed to determine neural cell viability. Atomic force microscopy (AFM) was used to quantify attached cell morphology and determine lamellipodia/ filopodia interaction with the surface of the semiconductor. It was seen that neurons show excellent viability, cell morphology, and good lamellipodia/ filopodia permissiveness when interacting with 3C-SiC. A neuronal activation device (NAD), based on the planar Michigan microelectrode probe, was constructed from 3C-SiC with the goal of activating an action potential within a neuron. In order to illicit an action potential, neurons were seeded on the NAD device and then they were subjected to a biphasic square pulse signal. Successful action potential activation was recorded through the use of Rhod-2, a Ca2+ sensitive fluorescent dye. Based on these results, 3C-SiC may be an excellent material platform for neural prosthetics.

Vascular smooth muscle cell migration is a microscopic in vivo process where specific cells crawl in order to partake in crucial physiological functions relating to embryonic development, wound healing, and tissue development. Abnormalities of cell migration result in pathologies such as tumor metastasis, angiogenesis, chronic inflammation, and various immune response dysfunctions. The mechanism behind cellular migration and the role of intracellular proteins in the instigation of cell directionality remains poorly understood without effective biomedical device available. The development of microfluidic biochips technologies enable detection, sample preparation and treatment on one single chip. We are reporting the design and fabrication of a novel microfluidic trip for guiding and quantifying cell migrations. The chip featured micropillar arrays imbedded in a multichannel microfluidic chip, where cell migration can be guided by utilizing the characteristics of laminar flow. Non-blending layers of fluid injected through the multi-channel device simulated a wounded edge across a monolayer of cells by limiting flow of trypsin, a serine protease, to half of the main channel, promoting cell migration in a desired direction. Control over cell directionality allows for the measurement and analysis of mechanical forces generated during cell migration in relation to migratory responses from intracellular protein inhibition. The micro-fluidic chip template was designed and manufactured using photolithography techniques. Polydimethylsiloxane (PDMS) served as the bulk material of the two compromising chip layers (channels and pillars), which were subsequently aligned and adhered to form the device. It was confirmed through both computer simulation and experimentation that the through optimized arrangement of the chip design, this device can effectively hold laminar flows of trypsin and cell media. Thus, this microfluidic device allows the user to simultaneously acquire force data during cell migration and observe migratory patterns to ultimately gain a better understanding of the underlying mechanisms of cell migration and directionality.

A novel immobilized metal affinity chromatography (IMAC) bead, Zr(IV)-immobilized resin, was prepared by surface template polymerization to enrich phosphorylated proteins and peptides from complex peptides mixtures. In order to enhance both the kinetics and the efficiency, large pathways for the proteins and peptides in the resin were formed, and the Zr(IV)-phosphate complexes were immobilized on the polymer surface. The morphology of the Zr(IV)-immobilized resin was evaluated the by measuring the specific surface area, pore volume, and pore distribution. The resin possessed large amount of the large-macro pores around 300 nm. The separation performance of β-casein from bovine serum albumin (BSA) solution was evaluated by phosphopeptide enrichment and MALDI-TOF MS analysis. The Zr(IV)-immobilized resin showed the high selectivity of the phosphopeptide.

This paper describes studies of patterned arrays on glass surfaces and their use as spatially separated reactors for in situ synthesis of DNA using an inkjet synthesizer. Photolithographic methods were employed to fabricate arrays composed of homogenous circular features containing a hydroxyl-terminated silane coupled to the surface of the glass via a siloxane bond. Features are embedded within a background matrix composed of a fluorosilane attached to the glass. Due to the differential wettability of the two silanes, whereby the hydroxyl-terminated silane and fluorosilane are hydrophilic and hydrophobic respectively because of their head groups, the patterned circular features are able to constrain liquid within a defined site. The silanization result was analyzed using X-ray photoelectron spectroscopy (XPS) to optimize silanization time and solvent. Synthesis was then performed using a custom-built inkjet system using phosphoramidite chemistry. Base-by-base analysis using fluorescent labeling showed consistent coupling efficiency on synthesis of a 50-mer homopolymer.

Nanodiamonds (NDs) have desirable chemical, physical and biological properties that lend them to a wide range of applications. ND’s facile surface chemistry, for example, can be used to create a high affinity for adsorbing various biological molecules. However, NDs, which are commercially available from multiple vendors, show inconsistencies with surface groups, aggregate sizes and impurity contents that may limit adsorption. We explore adsorption mechanisms of molecules to NDs in efforts to expand ND applications to drug delivery agents, bio-labels and enterosorbents. In doing so, several types of NDs and modification methods are evaluated to increase adsorption capacity and selectivity of propidium iodide and aflatoxin B1. Capacities and binding strengths of target molecules are assessed by Langmuir isotherms and transform calculations. UV-Vis spectroscopy shows our modification treatments are successful in increasing ND adsorption capacities. Additionally, cyclic voltammetry measurements, used to monitor in-situ adsorption, show electrochemical detection even after binding.

High resolution solid state NMR experiments were carried out on several compounds, to see how this technique can now be used to investigate in detail the surface structure of different biomaterials. First, because the surface of titanium implants can be functionalized by phosphonic acids, for instance to prevent bacterial adhesion,17O NMR experiments were performed on model TiO2 surfaces functionalized by 17O enriched phosphonic acids, to look at the mode of grafting of these coupling agents. Results bring clear evidence of the formation of Ti-O-P bridges and of the presence of residual P=O and P-OH groups. Second, given that calcium phosphates are widely present in biological hard tissues and synthetic biomaterials, 43Ca correlation experiments were performed on 43Ca enriched materials (hydroxyapatite and calcium benzoate), to see how the proximities between this nucleus and neighbouring atoms can be analyzed. Results show that both Ca…C and Ca…H proximities can be evidenced, and could thus help elucidate interface structures. All in all, these studies should pave the way to future investigations of biomaterials, and in particular of the structure of organic-inorganic interfaces.

Changes in protein glycosylation have great potential as markers for the early diagnosis of cancer and other diseases. The current analytical tools for the analysis of glycan structures need expensive instrumentation, advanced expertise, is time consuming and therefore not practical for routine screening of glycan biomarkers from human samples in a clinical setting.

We are developing a novel ultrasensitive diagnostic platform called ‘NanoMonitor’ to enable rapid label-free glycosylation analysis. The technology is based on electrochemical impedance spectroscopy where capacitance changes are measured at the electrical double layer interface as a result of interaction of two molecules.

The NanoMonitor platform consists of a printed circuit board with array of electrodes forming multiple sensor spots. Each sensor spot is overlaid with a nanoporous alumina membrane that forms a high density of nanowells. Lectins, proteins that bind to and recognize specific glycan structures, are conjugated to the surface of nanowells. When specific glycoproteins from a test sample bind to lectins in the nanowells, it produces a perturbation to the electrical double layer at the solid/liquid interface at the base of each nanowell. This perturbation results in a change in the impedance of the double layer which is dominated by the capacitance changes within the electrical double layer.

The nanoscale confinement or crowding of biological macromolecules within the nanowells is likely to enhance signals from the interaction of glycoproteins with the lectins leading to a high sensitivity of detection with the NanoMonitor as compared to other electrochemical techniques.

Using a panel of lectins, we were able to detect subtle changes in the glycosylation of fetuin protein as well as differentiate glycoproteins from normal versus cancerous cells. Our results indicate that NanoMonitor can be used as a cost-effective miniature electronic biosensor for the detection of glycan biomarkers.

We developed a BioMEMS device to study cell- mitochondrial physiological functionalities. The pathogenesis of many diseases including obesity, diabetes, heart failure as well as aging has been linked to functional defects of mitochondria. This is understandable as the mitochondria produces up to 90% of ATP, and plays a critical role in cell signaling and apoptosis. The synthesis of ATP is determined by the electrical potential across the inner mitochondrial membrane (IMM) and by the pH difference due to proton flux across it. Therefore, electrical characterization by E-fields with complementary chemical testing was used here. Mitochondrial ion channels present in the IMM control specific ion fluxes, and maintain ion homeostasis, matrix volume, IMM potential etc and thus serve a central role in cell growth and death related processes. Defects in ion channels (Channelopathies) are being attributed to many diseases like cancer, neurodegeneration, etc. Complete physiological roles of various ion channels and their interactions are still unknown, hindering the development of targeted therapeutic agents. The BioMEMS device was fabricated as an SU-8 based microfluidic system with gold electrodes on SiO2/Si wafers for electromagnetic interrogation. Ion Sensitive Field Effect Transistors (ISFETs) were incorporated for proton studies important in electron transport chain, together with monitoring Na+, K+, Ca++ions for ion channel studies. ISFETs are chemically sensitive MOSFET devices, their threshold voltage is directly proportional to the electrolytic H+ ion variation. These ISFETs (sensitivity ˜55 mV/pH for H+) were further realized as specific ion sensitive CHEMFETs by depositing a poly-HEMA layer sandwiched between the gate and a final specific ion sensitive membrane. Electrodes for dielectric spectroscopy studies of mitochondria were designed as 2- and 4-probe structures for optimized operation over a wide frequency range. In addition, to limit polarization effects (which masks actual impedance for high conductivity solutions at low frequencies), a 4-electrode set-up with unique meshed pickup electrodes (7.5×7.5 μm2 loops with 4 μm wires) was fabricated. An electrical model was developed for the mitochondrial sample, and its frequency response correlated with impedance spectroscopy experiments of sarcolemmal mitochondria. Using the mesh electrode structure, we obtained a reduction of 83.28% in impedance at 200 Hz. COMSOL simulations of selected electrical structures in this sensor were compared with experimental results to better understand the physical system. The simultaneous measurement of membrane potential, ion concentrations and pH would enhance diagnostics and studies of mitochondrial diseases.

Flat coupons prepared from cobalt chromium alloy (CoCr) were modified using different methods (low energy excimer laser processing, electron beam irradiation, and immobilized covalently-bound heparin coating). Human coronary artery endothelial cell (HCAEC) attachment and growth kinetics were investigated on unmodified and modified metal surfaces. Results showed that HCAEC attach to unmodified CoCr coupons and surface-modified CoCr coupons. No change in cell number was observed when cells were grown on CoCr coupons and heparin coated coupons throughout the 72h study period. A decrease in cell number was observed for excimer treated coupons. HCAEC seeding on CoCr stents indicated that cells attached and proliferated on the stents over a ten day study period. This research showed that physical modifications did not improve cell proliferation. Very few non-viable cells were observed for unmodified and surface bound heparin coupons, and cells attached to the surface up to 72h. This shows that heparin can be coated on a stent surface to provide anti-thrombotic properties without any negative effect on cell attachment and proliferation. In vitro screening method of testing endothelial cell attachment and proliferation on modified metal stent surfaces can be used to gain insight for developing next generation drug eluting stents with improved endothelialization behavior.

A powerful fabrication platform for a wide range of biomimetic, high-aspect-ratio nanostructured surfaces is introduced. The principles of soft lithography are extended into a double-mold replication process, whereby a master topography is mapped onto an elastomeric inverse mold and replicated in arbitrary multiple material and stiffness gradients, and an array of modified geometries. Control of geometry via deformation of the inverse mold and control of stiffness via prepolymer mixing are discussed. New capabilities enabled by our approach include biomimetic actuation/sensor arrays with programmable biases, precisely tunable mechanical and geometric properties for optical or wetting applications, and flexible curved substrates. Indeed, flexibly anchored ciliary high-aspect-ratio nanostructures are now possible, and a proof-of-principle is described.

Current trends in sensing and diagnostics is towards developing hybrid devices that incorporate nanomaterial for enhancing device performance. These devices and systems have a broad impact ranging from personalized medicine in health care, environmental sensing and building multifunctional sensors for military applications. The overarching objective of the research work is to develop a new class of portable, bio-analytical tools with improved functionality and performance capabilities by utilizing the electrical effects on cellular and sub cellular species in micro and nanoscale domains.

There are two key ideas underlying this research work. The first is to design and manufacture structures comprising of nanoscale-confined spaces integrated on to multi-scale architecture platforms. This model architecture has been engineered to harness the principle of macromolecular crowding for biomolecule binding and detection by monitoring perturbations in the electrical bi-layer in tailored nanoscale confined spaces. Enhanced performance metrics in biomolecule detection have been demonstrated in developing electrical immunoassays. We have demonstrated picogram/ml sensitivity in detection of specific cardiovascular disease biomarkers, cancer biomarkers from human serum samples with a dynamic range of response varying from pg/ml to g/ml and response time within 120 seconds.

Studying how individual neuronal cells grow and interact with each other is of fundamental importance for understanding the functions of the nervous system. However, the mechanism of axonal navigation to their target region and their specific interactions with guidance factors such as membrane-bound proteins, chemical and temperature gradients, mechanical guidance cues, etc. are not well understood. Here we describe a new approach for controlling the adhesion, growth and interconnectivity of cortical neurons on Au surfaces. Specifically, we use Atomic Force Microscopy (AFM) nanolithography to immobilize growth-factor proteins at well-defined locations on Au surfaces. These surface-immobilized proteins act as a) adhesion proteins for neuronal cells (i.e. well-defined locations where the cells “stick” to the surface), and b) promoters/inhibitors for the growth of neurites. Our results show that protein patterns can be used to confine neuronal cells and to control their growth and interconnectivity on Au surfaces. We also show that AFM nanolithography presents unique advantages for this type of work, such as high degree of control over location and shape of the protein patterns, and application of proteins in aqueous solutions (protein buffers), such that the proteins are very likely to retain their folding conformation/bioactivity.