Label-Free Quartz Crystal Microbalance with Dissipation Monitoring of Resveratrol Effect on Mechanical Changes and Folate Receptor Expression Levels of Living MCF-7 Cells: A Model for Screening of Drugs

Monitoring phage infection and lysis of surface-immobilized bacteria by QCM-D

While being a promising approach for the treatment of infections caused by drug-resistant, pathogenic bacteria, the clinical implementation of phage therapy still faces several challenges. One of these challenges lies in the high strain-specificity of most bacteriophages, which makes it necessary to screen large phage collections against the target pathogens in order to identify suitable candidates for the formulations of personalized therapeutic phage cocktails. In this work, we evaluate the potential of quartz crystal microbalance with dissipation monitoring (QCM-D) to identify and detect phage infection and subsequent lysis of bacteria immobilized on the surfaces of the QCM-D sensors. Using lytic Escherichia coli phage T7 as a model, we show that phage infection of E. coli cells results in various unique alterations in the behaviors of the frequency (Δf) and dissipation (ΔD) signals, which are not observed during exposure of the E. coli strain to non-infectious Bacillus subtilis phage phi29 at similar concentration. To aid future phage screening campaigns, we furthermore identify a single measurement parameter, i.e., the spread between the different overtones of ΔD, that can be used to detect phage-induced lysis. For T7 infection of E. coli, this is achieved within 4 h after inoculation, including immobilization and growth of the bacteria on the sensor surface, as well as the completed phage propagation cycle. Given the commercial availability of highly automated multichannel systems and the fact that this approach does not require any sensor modifications, QCM-D has the potential to become a valuable tool for screening medium-sized phage collections against target pathogens.

Biophysical and Morphological Cell Features Retrieved by Digital Holographic Microscopy Correlate with Drug-Induced Changes in Cell Migration Behavior

Quantitative analysis of cancer cell migration is critical for developing effective therapies to curb cancer metastasis. However, traditional methods are time-consuming and labor-intensive and lack quantitative capabilities. Cell volume change, a key physiological indicator of cell migration, is directly linked to phase change. In this work, we have developed a model that connects phase features from digital holographic microscopy (DHM) with cell healrate values from the wound healing assay. This approach aims to provide a rapid and quantitative evaluation of the breast cancer cell migration capability. Using DHM, six phase features of 231 cells treated with varying drug concentrations were extracted. It was observed that the rate of change of these phase features, termed characteristic parameters, showed a high linear correlation with cell healrate values from wound healing assays. Based on these linear correlations, a composite coefficient was derived by linearly combining the characteristic parameters of the six phase features. This composite coefficient was then linearly correlated with the cell healrate values to create a correlation model. This model establishes a strong connection between DHM-extracted morphological/biophysical features and cell migration metrics from a complementary assay. It provides a new, rapid, and quantitative method for assessing cancer cell migration in vitro and delivering valuable insights for cancer research.

Dynamical and noninvasive monitoring of curcumin effect on the changes in the viscoelasticity of human breast cancer cells: A novel model to assess cell apoptosis

A real-time quartz crystal microbalance (QCM) cytosensor was first developed for dynamical and noninvasive monitoring of cell viscoelasticity for evaluation of apoptosis degree. In this work, human breast cancer cells MCF-7 and MDA-MB-231 were employed as cell model and respectively captured on the surface of QCM electrode modified with mercaptosuccinic acid and poly-l-lysine. Cell viscoelasticity was measured dynamically by real-time monitoring energy dissipation with QCM, and the dynamic diagram of the energy dissipation of MDA-MB-231 cells treated with curcumin was first obtained. The results displayed that the changes of energy dissipation in MDA-MB-231 cells and MCF-7 cells were 8.81 × 10^-6 and 5.29 × 10^-6, particularly due to the difference in cell viscoelasticity. Furthermore, curcumin was used to induce cell apoptosis and suppress energy dissipation of MDA-MB-231 cells. Combining apoptosis assay with QCM measurement, the results revealed good linear relationship between cell viscoelasticity inhibition and apoptosis rate with correlation coefficient R = 0.9908. The QCM cytosensor could rapidly, accurately, dynamically, and noninvasively monitor the changes of cell viscoelasticity for evaluation of apoptosis degree in MDA-MB-231 cells. The study established a new model for cell apoptosis assessment, facilitating understanding of the mechanisms of cell apoptosis on the aspect of mechanical properties.

Pentagalloyl Glucose-Laden Poly(lactide-co-glycolide) Nanoparticles for the Biomechanical Extracellular Matrix Stabilization of an In Vitro Abdominal Aortic Aneurysm Model

The suppression of abdominal aortic aneurysm (AAA) growth by nonsurgical therapy is currently not an option, and AAA is considered an irreversible destructive disease. The formation and development of AAA is associated with the progressive deterioration of the aortic wall. Infiltrated macrophages and resident vascular smooth muscle cells oversecrete matrix metalloproteinases (MMPs), which cause the loss of crucial aortic extracellular matrix (ECM) components, thus weakening the aortic wall. Stabilization of the aortic ECM could enable the development of novel therapeutic options for preventing and reducing AAA progression. In the present work, we studied the biochemical and biomechanical interactions of pentagalloyl glucose (PGG) on mouse C2C12 myoblast cells. PGG is a naturally occurring ECM-stabilizing polyphenolic compound that has been studied in various applications, including vascular health, with promising results. With its known limitations of systemic administration, we also studied the administration of PGG when encapsulated within poly(lactide-co-glycolide) (PLGA) nanoparticles (NPs). Treatment with collagenase and elastase enzymes was used to mimic a pathway of degenerative effects seen in the pathogenesis of human AAA. PGG and PLGA(PGG) NPs were added to enzyme-treated cells in either a suppressive or preventative scenario. Biomolecular interactions were analyzed through cell viability, cell adhesion, reactive oxygen species (ROS) production, and MMP-2 and MMP-9 secretion. Biomechanical properties were studied through atomic force microscopy and quartz crystal microbalance with dissipation. Our results suggest that PGG or PLGA(PGG) NPs caused minor to no cytotoxic effects on the C2C12 cells. Both PGG and PLGA(PGG) NPs showed reduction in ROS and MMP-2 secretion if administered after enzymatic ECM degradation. A quantitative comparison of Young's moduli showed a significant recovery in the elastic properties of the cells treated with PGG or PLGA(PGG) NPs after enzymatic ECM degradation. This work provides preliminary support for the use of a pharmacological therapy for AAA treatment.

Two-dimensional nanocomposite-based electrochemical sensor for rapid determination of trans-resveratrol

A two-dimensional nanocomposite-based disposable electrochemical sensor was fabricated for the rapid analysis of trans-resveratrol (TRA) in red wine. The sensor was prepared by modifying graphene-molybdenum disulfide (Gr-MoS₂) nanocomposite on the surface of screen-printed electrode (SPE). Results show that the Gr-MoS₂ nanocomposite with sheet-on-sheet structure can accelerate the oxidation reaction kinetics of TRA due to its large effective electrochemical surface area and high electron transfer rate. As a result, the Gr-MoS₂ nanocomposite appears the synergistic effects, making the highly sensitive detection of TRA come true. The prepared sensor showed a linear response in TRA concentration from 1.0 to 200 μmol L^-1 (with a limit of detection of 0.45 μmol L^-1). After validating the accuracy with high performance liquid chromatography (HPLC), this nanocomposite-based electrochemical sensor can be applied for the detection of TRA in real red wine samples.

Evaluation of trans-resveratrol level in grape wine using laser-induced porous graphene-based electrochemical sensor

trans-Resveratrol (TRA), is one of the indicators to evaluate the quality of red wines. In this study, a novel flexible electrochemical sensor using direct laser-induced graphene (LIG) technique that transforms the commercial Kapton tape into three-dimensional (3D) porous graphene was developed for sensitive detection of TRA molecules in red wines. For the first time, the strategy of 'double layer' (Kapton/polyimide) was employed to obtain the LIG with undamaged shape and excellent electrical properties. The mechanism of heat absorption and dissipation of laser-induced process was investigated in detail. The prepared electrochemical sensor with excellent repeatability, stability, reproducibility, and reliability, appears an excellent linear response within the TRA concentration range from 0.2 to 50 μmol L^-1 and a low limit of detection (LOD) of 0.16 μmol L^-1. Furthermore, the developed sensor can be applied for the evaluation of TRA level in red wines and grape skins with a satisfactory result. The sensor may be potential in analysis of active compounds in food or environmental samples.

Relating the rate of growth of metal nanoparticles to cluster size distribution in electroless deposition

Electroless deposition on patterned silicon substrates enables the formation of metal nanomaterials with tight control over their size and shape. In the technique, metal ions are transported by diffusion from a solution to the active sites of an autocatalytic substrate where they are reduced as metals upon contact. Here, using diffusion limited aggregation models and numerical simulations, we derived relationships that correlate the cluster size distribution to the total mass of deposited particles. We found that the ratio ξ between the rates of growth of two different metals depends on the ratio γ between the rates of growth of clusters formed by those metals through the linearity law ξ = 14(γ - 1). We then validated the model using experiments. Different from other methods, the model derives k using as input the geometry of metal nanoparticle clusters, decoded by SEM or AFM images of samples, and a known reference.

Quartz Crystal Microbalance With Dissipation Monitoring: A Powerful Method to Predict the in vivo Behavior of Bioengineered Surfaces

The Quartz Crystal Microbalance with dissipation monitoring (QCM-D) is a tool to measure mass and viscosity in processes occurring at or near surfaces, or within thin films. QCM-D is able to detect extremely small chemical, mechanical, and electrical changes taking place on the sensor surface and to convert them into electrical signals which can be investigated to study dynamic process. Surface nanotopography and chemical composition are of pivotal importance in biomedical applications since interactions of medical devices with the physiological environment are mediated by surface features. This review is intended to provide readers with an up-to-date summary of QCM-D applications in the study of cell behavior and to discuss the future trends for the use of QCM-D as a high-throughput method to study cell/surface interactions overcoming the current challenges in the design of biomedical devices.

The Exploration and Confirmation of the Maximum Mass Sensitivity of Quartz Crystal Microbalance

After the advent of the quartz crystal microbalance (QCM) technology, various QCM-based sensing systems have got certain applications in many science and technology fields and resulted in dramatic progress in these fields. The core advantage of QCM is its high mass sensitivity which leads to high accuracy and low detection limit. For a QCM, the mass sensitivity is determined by the diameter and thickness of the electrode to a certain extent when the frequency of the quartz wafer is already determined. Theoretical approximate calculation reveals that there is an optimum electrode diameter corresponding to the maximum sensitivity. This is different from the traditional opinion that the smaller the electrode, the higher the mass sensitivity. A plating experiment was carried out using 28 QCMs with different electrode diameters, and the experimental results verified the existence of the optimum diameter. This study is helpful to obtain higher mass sensitivity by optimizing electrode parameters.

Label-free optical biosensor for real-time monitoring the cytotoxicity of xenobiotics: A proof of principle study on glyphosate

Rapid and inexpensive biosensor technologies allowing real-time analysis of biomolecular and cellular events have become the basis of next-generation cell-based screening techniques. Our work opens up novel opportunities in the application of the high-throughput label-free Epic BenchTop optical biosensor in cell toxicity studies. The Epic technology records integrated cellular responses about changes in cell morphology and dynamic mass redistribution of cellular contents at the 100-150 nm layer above the sensor surface. The aim of the present study was to apply this novel technology to identify the effect of the herbicide Roundup Classic, its co-formulant polyethoxylated tallow amine (POEA), and its active ingredient glyphosate, on MC3T3-E1 cells adhered on the biosensor surface. The half maximal inhibitory concentrations of Roundup Classic, POEA and glyphosate upon 1 h of exposure were found to be 0.024%, 0.021% and 0.163% in serum-containing medium and 0.028%, 0.019% and 0.538% in serum-free conditions, respectively (at concentrations equivalent to the diluted Roundup solution). These results showed a good correlation with parallel end-point assays, demonstrating the outstanding utility of the Epic technique in cytotoxicity screening, allowing not only high-throughput, real-time detection, but also reduced assay run time and cytotoxicity assessment at end-points far before cell death would occur.

Quartz Crystal Microbalance with Approximately Uniform Sensitivity Distribution

The nonuniformity of QCMs' mass sensitivity distribution is a disadvantage to practical applications. Through theoretical calculations, we found that common ring electrode QCMs could obtain approximately uniform sensitivity distribution by carefully selecting the inner and outer diameters and mass loading factor of the electrode. A series of experiments were carried out using 10 MHz ring electrode QCMs with an inner diameter of 2 mm, an outer diameter of 5 mm, and a loading factor R of 0.0044. The experimental results proved that its mass sensitivity distribution is approximately uniform. This special designed ring electrode QCMs is suitable and convenient for highly accurate measurements.

Controlled synthesis of mixed molecular nanostructures from folate and deferrioxamine-Ga(III) on gold and tuning their performance for cancer cells

A new strategy is developed for construction of the mixed molecular nanostructures from folic acid (FOA), a targeting agent, and deferrioxamoine-Ga(III), (DFO-Ga(III)), a theranostic agent, on gold-mercaptopropionic acid surface, Au-MPA. The strategy is focused to achieve a system in which all the active constituents of FOA; i.e., pteridine rings, p-aminobenzoeic acid, and the glutamic acid, having high affinity for folate receptor overexpressed on cancer cells; remain unreacted in adjacent to DFO-Ga(III), Au-MPA-[DFO-Ga(III)]‖-[FOA]. For this purpose, the NH₂ groups of FOA and DFO-Ga(III) were attached covalently and separately to COOH of Au-MPA surface allowing all the active groups of FOA to be available for drug delivery purposes. The data obtained through several electrochemical and surface analysis techniques, supported successful construction of the designed mixed molecular nanostructures system. In addition, the results showed that the system is stable, and Ga(III) ion does not leave DFO-Ga(III) complex. The prepared surface was successfully tested for capturing of the breast cancer cells 4T1 as a model. The measurements showed a rapid uptake kinetics (t_1/2 of ~6.0min) and efficient accessibility of the system by the cancer cells; the R_ct was significantly increased in the presence of 4T1 cells compared with blank PBS (ΔR_ct ~420kΩ).

Unfound Associated Resonant Model and Its Impact on Response of a Quartz Crystal Microbalance in the Liquid Phase

Quartz crystal microbalance (QCM) is an important tool to detect in real time the mass change at the nanogram level. However, for a QCM operated in the liquid phase, the Sauerbrey equation is usually disturbed by the changes in liquid properties and the longitudinal wave effect. Herein, we report another unfound associated high-frequency resonance (HFR) model for the QCM, with the intensity 2 orders of magnitude higher than that of the fundamental peak in the liquid phase. The HFR model exhibits obvious impact on the response of QCM in the thickness-shear model (TSM), especially for overtones. The frequency of HFR peak is decreased dramatically with increasing conductivity or permittivity of the liquid phase, resulting in considerable additional frequency shifts in the TSM as baseline drift. Compared to that with a faraway HFR peak, the overlapping of HFR peak to a TSM overtone results in the frequency shifts of ±50-70 kHz with its intensity enhancement by 3 orders of magnitude in the later. The HFR behavior is explained by an equivalent circuit model including leading wire inductance, liquid inductance, and static capacitance of QCM. Taking into account the HFR model, the positive frequency shifts of the QCM at high overtones during the cell adhesion process is understandable. Combining the TSM and HFR is an effective way to improve the stability of QCM and provides more reliable information from the responses of QCM. The HFR may have potential application in chemical and biological sensors.

Overcoming multiple gastrointestinal barriers by bilayer modified hollow mesoporous silica nanocarriers

Oral administration of nanocarriers remains a significant challenge in the pharmaceutical sciences. The nanocarriers must efficiently overcome multiple gastrointestinal barriers including the harsh gastrointestinal environment, the mucosal layer, and the epithelium. Neutral hydrophilic surfaces are reportedly necessary for mucus permeation, but hydrophobic and cationic surfaces are important for efficient epithelial absorption. To accommodate these conflicting surface property requirements, we developed a strategy to modify nanocarrier surfaces with cationic cell-penetrating peptides (CPP) concealed by a hydrophilic succinylated casein (SCN) layer. SCN is a mucus-inert natural material specifically degraded in the intestine, thus protecting nanocarriers from the harsh gastric environment, facilitating their mucus permeation, and inducing exposure of CPPs after degradation for further effective transepithelial transport. Quantum dots doped hollow silica nanoparticles (HSQN) with a diameter around 180 nm was used as the nanocarrier and demonstrated as high as 50% loading efficacy of paclitaxel, a model drug with poor solubility and permeability. The dual layer modification strategy prevented premature drug leakage in stomach and maintained high mucus permeation (the trajectory spanned 9-fold larger area than single CPP modification). After intestinal degradation of SCN by trypsin, these nanocarriers exhibited strong interaction with epithelial membranes and a 5-fold increase in cellular uptake. Significant transepithelial transport and intestinal distribution were also observed for this dual-modified formulation. A pharmacokinetics study on the paclitaxel-loaded nanocarrier found 40% absolute bioavailability and 7.8-fold higher AUC compared to oral Taxol®. Compared with single CPP modified nanocarriers, our formulation showed increased in vivo efficacy and tumor accumulation of the model drug with negligible intestinal toxicity. In summary, sequential modification with CPP and SCN layers on HSQN offers a potential strategy to overcome the multiple barriers of the gastrointestinal tract.

STATEMENT OF SIGNIFICANCE

Oral administration of nanocarriers remains a big challenge due to the multiple gastrointestinal barriers. In order to achieve both strong mucus permeation and efficient epithelial absorption, we modified the surface of silica nanoparticles with two layers: cell penetrating peptide (CPP) layer and succinylated casein (SCN) layer. The newly developed nanoformulations are demonstrated to have the following advantages: 1) versatile carrier with easy preparation, 2) high drug loading especially for poor soluble molecules, 3) reduced drug leakage in the stomach, 4) effective mucus penetration and transepithelial transport and 5) good biocompatibility, which in all indicate a great potential of this bilayer-modification strategy to facilitate the oral delivery of therapeutic agents.

Electrochemical Evaluation of trans-Resveratrol Levels in Red Wine Based on the Interaction between Resveratrol and Graphene

trans-Resveratrol is often considered as one of the quality standards of red wine, and the development of a sensitive and reliable method for monitoring the trans-resveratrol levels in red wine is an urgent requirement for the quality control. Here, a novel voltammetric approach was described for probing trans-resveratrol using a graphene-modified glassy carbon (GC) electrode. The proposed electrode was prepared by one-step electrodeposition of reduced graphene oxide (ERGO) at a GC electrode. Compared with the bare GC electrode, the introduced graphene film on the electrode surface dramatically improved the sensitivity of the sensor response due to the π-π interaction between the graphene and trans-resveratrol. The developed sensor exhibited low detection limit of 0.2 μM with wide linear range of 0.8-32 μM and high stability. For the analysis of trans-resveratrol in red wine, the high anti-interference ability and the good recoveries indicated the great potential for practical applications.

A CD44-biosensor for evaluating metastatic potential of breast cancer cells based on quartz crystal microbalance

A sensitive CD44-biosensor based on quartz crystal microbalance (QCM) was proposed for evaluating metastatic potential of breast cancer cells by using hyaluronan (HA) functionalized substrate film, polydopamine and polyethyleneimine composite film, for the purpose of capturing CD44-positive cancer cells through specific binding of HA to CD44. Two differently CD44-expressed breast cancer cell lines (MDA-MB-231 cells and MCF-7 cells) were put to use as targets for quantitative analysis as well as evaluation of metastatic potential of the cells. The limit of detection for MDA-MB-231 (M231) cells and MCF-7 cells were 300 and 1,000cellsmL^-1, respectively. The expression level of CD44 on M231 cells exhibited two times higher than that of MCF-7 cells, indicating of a higher metastatic potential. Moreover, poly-L-lysine modified QCM sensor was applied to monitor the stiffness of breast cancer cells that can reflect metastatic potential of cells. The results revealed that the MCF-7 cells were stiffer than M231 cells, implying that the M231 cells possessed higher metastatic potential. The proposed protocol is simple and rapid to evaluate the metastatic potential of cancer cells, in addition to offering a promising diagnostic tool for metastatic cancer.

Quartz-Crystal Microbalance (QCM) for Public Health: An Overview of Its Applications

Nanobiotechnologies, from the convergence of nanotechnology and molecular biology and postgenomics medicine, play a major role in the field of public health. This overview summarizes the potentiality of piezoelectric sensors, and in particular, of quartz-crystal microbalance (QCM), a physical nanogram-sensitive device. QCM enables the rapid, real time, on-site detection of pathogens with an enormous burden in public health, such as influenza and other respiratory viruses, hepatitis B virus (HBV), and drug-resistant bacteria, among others. Further, it allows to detect food allergens, food-borne pathogens, such as Escherichia coli and Salmonella typhimurium, and food chemical contaminants, as well as water-borne microorganisms and environmental contaminants. Moreover, QCM holds promises in early cancer detection and screening of new antiblastic drugs. Applications for monitoring biohazards, for assuring homeland security, and preventing bioterrorism are also discussed.

Quantification of cell viability and rapid screening anti-cancer drug utilizing nanomechanical fluctuation

Cancer is a serious threat to human health. Although numerous anti-cancer drugs are available clinically, many have shown toxic side effects due to poor tumor-selectivity, and reduced effectiveness due to cancers rapid development of resistance to treatment. The development of new highly efficient and practical methods to quantify cell viability and its change under drug treatment is thus of significant importance in both understanding of anti-cancer mechanism and anti-cancer drug screening. Here, we present an approach of utilizing a nanomechanical fluctuation based highly sensitive microcantilever sensor, which is capable of characterizing the viability of cells and quantitatively screening (within tens of minutes) their responses to a drug with the obvious advantages of a rapid, label-free, quantitative, noninvasive, real-time and in-situ assay. The microcantilever sensor operated in fluctuation mode was used in evaluating the paclitaxel effectiveness on breast cancer cell line MCF-7. This study demonstrated that the nanomechanical fluctuations of the microcantilever sensor are sensitive enough to detect the dynamic variation in cellular force which is provided by the cytoskeleton, using cell metabolism as its energy source, and the dynamic instability of microtubules plays an important role in the generation of the force. We propose that cell viability consists of two parts: biological viability and mechanical viability. Our experimental results suggest that paclitaxel has little effect on biological viability, but has a significant effect on mechanical viability. This new method provides a new concept and strategy for the evaluation of cell viability and the screening of anti-cancer drugs.