In Situ Regeneration of Silicon Microring Biosensors Coated with Parylene C.

Optical biosensors support disease diagnostic applications, offering high accuracy and sensitivity due to label-free detection and their optical resonance enhancement. However, optical biosensors based on noble metal nanoparticles and precise micro-electromechanical system technology are costly, which is an obstacle for their applications. Here, we proposed a biosensor reuse method with nanoscale parylene C film, taking the silicon-on-insulator microring resonator biosensor as an example. Parylene C can efficiently adsorb antibody by one-step modification without any surface treatment, which simplifies the antibody modification process of sensors. Parylene C (20 nm thick) was successfully coated on the surface of the microring to modify anti-carcinoembryonic antigen (anti-CEA) and specifically detect CEA. After sensing, parylene C was successfully removed without damaging the sensing surface for the sensor reusing. The experimental results demonstrate that the sensing response did not change significantly after the sensor was reused more than five times, which verifies the repeatability and reliability of the reusable method by using parylene C. This framework can potentially reduce the cost of biosensors and promote their further applications.

Controllable bisubstrate multi-colorimetric assay based on peroxidase-like nanozyme and complementary colorharmonic principle for semi-quantitative detection of H2O2 with the naked eye.

Naked-eye semi-quantitative (NEQ) assays should exhibit vivid color variations and one-to-one correspondence between the analyte concentrations and the color display. Herein, we report a bisubstrate multi-colorimetric system, constituted by 3,3',5,5'-tetramethylbenzidine (TMB) and dopamine (DA), which carries out a controllable NEQ assay based on the complementary colorharmonic principle. This bisubstrate system is a universal threshold NEQ assay with tunable sensitivity and detection window depending on the H2O2 concentration. The peroxidase-like activity of PEG@Fe3O4 NPs was used to catalyze the oxidations of TMB and DA by H2O2 to the colored products. On the basis of UV-vis spectra data, it was speculated that the oxidation product of TMB (TMB·+) could oxidize DA in this system. The concentration of DA controls the consumption of oxidant (H2O2) and the oxidation of TMB. By controlling the molar ratio of TMB to DA, the bisubstrate system precisely showed multicolor displays (e.g., three-color display: orange, gray, and blue) at submillimolar and millimolar concentrations of H2O2. The detection limit and sensitivity for H2O2 were 0.4 mM and 0.1 mM, respectively. Next, the system was applied to the threshold detection of hypoglycemia (orange), normal (gray), and hyperglycemia (blue) in spiked samples on both gel- and paper-based test strips. Digitalized colorimetric results using the red-green-blue (RGB) analysis with smartphone application were achieved. This work provides a new strategy of multi-colorimetric assay that takes advantages of controllability, threshold detection, vivid color variations, and reproducibility (CVs were 1.1-2.1%), which could be potentially useful for in-field and point-of-care applications.

[Intraocular Pressure Sensor Based on a Contact Lens].

Intraocular pressure detection has a great significance for understanding the status of eye health, prevention and treatment of diseases such as glaucoma. Traditional intraocular pressure detection needs to be held in the hospital. It is not only time-consuming to doctors and patients, but also difficult to achieve 24 hour-continuous detection. Microminiaturization of the intraocular pressure sensor and wearing it as a contact lens, which is convenient, comfortable and noninvasive, can solve this problem because the soft contact lens with an embedded micro fabricated strain gauge allows the measurement of changes in corneal curvature to correlate to variations of intraocular pressure. We fabricated a strain gauge using micro-electron mechanical systems, and integrated with the contact lens made of polydimethylsiloxane (PDMS) using injection molding. The experimental results showed that the sensitivity was 100. 7 µV/µm. When attached to the corneal surface, the average sensitivity of sensor response of intraocular pressure can be 125.8 µV/mm Hg under the ideal condition.

An integrated device for patterning cells and selectively detaching.

Cell detachment is an ordinary cell behavior, and acts a significant role in numerous physiological processes. In addition, as massive cell groups have specific shapes in vivo, selectively controlling detachment of patterned cells is crucial for both clinical and fundamental research, because it may act as a platform for studying many processes in vitro, and also may be used for tissue engineering. However, it is difficult to first pattern cell groups into isolated islands and then to control their detachment dynamically. Herein, we developed an integrated device that could confine cell groups into various designed shapes, and selectively detach them by applying a low potential. This device contains electrode arrays (EAs) for cell pattern and detachment; and an automatic control system (ACS) connected to a computer for electrically controlling cell detachment. By microfabrication technology, EAs are fabricated on a glass substrate and isolated by surrounding insulating layer (Parylene-C). A new surface modification method is developed: within one step, oligopeptide (CCRRGDWLC) can bond to the gold surface of EAs for cell adhesion or detachment, and PLL-PEG grafts to other parts around the gold surface to resist cell adhesion simultaneously. When a low potential is applied by the ACS to the selected electrodes, cell groups on these electrodes would round up and detach from the surface. Comparing with previous methods, our method can first pattern cells and then selectively detach them. Besides, this device is easy to operate, fast response, and the detaching units are high through-put, and we believe it will be widely used in biological and medical labs.

An efficient photothermal-chemotherapy platform based on a polyacrylamide/phytic acid/polydopamine hydrogel.

In this work, the polyacrylamide/phytic acid/polydopamine (termed as PAAM/PA/PDA) hydrogel is used as a drug loading matrix and photothermal conversion reagent, which is prepared by copolymerization of dopamine with acrylamide through a phytic acid crosslinker. Due to the porous structure of PAAM and strong near-infrared light (NIR)-absorption of PDA, the PAAM/PA/PDA hydrogel exhibits a high doxorubicin (DOX)-loading capacity (170 mg g-1) and efficient photothermal transduction efficiency (47.4%) even under low power density 808 nm NIR laser (0.75 W cm-2) irradiation, which is superior to those of most conventional photothermal conversion agents reported in the literature. With NIR laser irradiation, the PAAM/PA/PDA hydrogel loaded with DOX (termed as PAAM/PA/PDA/DOX) shows excellent synergistic interaction between photothermal therapy (PTT) and enhanced chemotherapy, resulting in the completely suppressed growth of mouse-bearing SW620 tumors. Furthermore, the PAAM/PA/PDA hydrogel shows good physicochemical stability, negligible cytotoxicity and low toxicity in vivo. All these characteristics render the as-prepared PAAM/PA/PDA hydrogel promising for biomedical applications.

The controllable growth of ultrathin MnO2 on polydopamine nanospheres as a single nanoplatform for the MRI-guided synergistic therapy of tumors.

The integration of two-dimensional (2D) nanosheets with biocompatible photothermal nanoparticles may produce effective multifunctional nanotheranostic agents. However, such explorations are hindered due to the lack of suitable methods for the incorporation of both materials. In this work, a simple redox strategy was designed for the controllable growth of ultrathin manganese dioxide nanosheets on polydopamine nanospheres. After loading with methylene blue, the obtained polydopamine@ultrathin manganese dioxide/methylene blue nanoflowers (termed PDA@ut-MnO2/MB NFs) show excellent multiple capabilities for tumor synergistic therapy, for instance: (1) they efficiently modulate the tumor microenvironment (TME) via the generation of O2 and the depletion of glutathione (GSH); (2) they demonstrate favorable photothermal effects during PTT to speed up intratumoral blood flow and chemical reactions, enhancing oxygen distribution and synergistically increasing PDT efficacy; and (3) they support ultrasensitive reduction-responsive magnetic resonance imaging (MRI). Using mice bearing HCT116 colorectal tumors as a model system, PDA@MnO2/MB NFs were shown to achieve near-complete suppression of tumor growth following MRI-guided PDT/PTT synergistic therapy.

Construction of lanthanide-doped upconversion nanoparticle-Uelx Europaeus Agglutinin-I bioconjugates with brightness red emission for ultrasensitive in vivo imaging of colorectal tumor.

Lanthanide-doped upconversion nanoparticles (UCNPs)-based active targeting optical bioimaging has attracted tremendous scientific interest because of its noninvasive real-time signal feedback, superior tissue penetration depth and high spatial resolution in early diagnosis of disease. Herein, we synthesize a novel carboxy-terminated silica coated NaErF4: 10% Yb@NaYF4: 40% Yb@NaNdF4: 10% Yb@NaGdF4: 20% Yb UCNPs (termed as UCNP@SiO2-COOH) with 808 nm near-infrared (NIR) excitation and bright 655 nm upconversion luminescence (UCL) emission for realizing deep tissue imaging. Under 808 nm NIR laser excitation (1.5 W cm-2), the UCL of UCNP@SiO2-COOH with relative low concentration (2 mg mL-1) can be successfully visualized under a chicken breast slice with 10 mm thickness. After conjugated with various molecules including NH2-PEG3400-COOH, peptide D-SP5 and Uelx Europaeus Agglutinin-I (UEA-I), biodistributions, clearance pathways and tumor-targeting capacities of the UCNP@SiO2-COOH and corresponding bioconjugates (termed as UCNP@SiO2-PEG, UCNP@SiO2-D-SP5 and UCNP@SiO2-UEA-I, respectively) were investigated by tracking the UCL intensities of livers, kidneys and tumors. Both of in vitro and in vivo experimental results reveal that there is no significant difference for their in vivo biodistributions and clearance pathways. The UCNP@SiO2-UEA-I exhibits much higher SW480 tumor-targeting capacity than those of other bioconjugates. In particular, the as-prepared UCNP@SiO2-UEA-I even to visualize ultrasmall (c.a. 3 mm3 in volume) subcutaneous SW480 tumor in Balb/c nude mouse through intravenous administration. The study implies that the red UCL emitted UCNPs with a minimized heating effect is suitable for deep tissue biomedical imaging and UCNP@SiO2-UEA-I can serve as an efficient optical probe for early diagnosis of SW480 tumor.

A PDMS Device Coupled with Culture Dish for In Vitro Cell Migration Assay.

Cell migration and invasion are important factors during tumor progression and metastasis. Wound-healing assay and the Boyden chamber assay are efficient tools to investigate tumor development because both of them could be applied to measure cell migration rate. Therefore, a simple and integrated polydimethylsiloxane (PDMS) device was developed for cell migration assay, which could perform quantitative evaluation of cell migration behaviors, especially for the wound-healing assay. The integrated device was composed of three units, which included cell culture dish, PDMS chamber, and wound generation mold. The PDMS chamber was integrated with cell culture chamber and could perform six experiments under different conditions of stimuli simultaneously. To verify the function of this device, it was utilized to explore the tumor cell migration behaviors under different concentrations of fetal bovine serum (FBS) and transforming growth factor (TGF-ß) at different time points. This device has the unique capability to create the "wound" area in parallel during cell migration assay and provides a simple and efficient platform for investigating cell migration assay in biomedical application.

Evaluation of Matrix Metalloproteinase Inhibition by Peptide Microarray-Based Fluorescence Assay on Polymer Brush Substrate and in Vivo Assessment.

Matrix metalloproteinases (MMPs) are important biomarkers and potential therapeutic targets of tumor. In this report, a peptide microarray-based fluorescence assay is developed for MMPs inhibitors evaluation through immobilization of biotin-modified peptides on the poly(glycidyl methacrylate-co-2-hydroxyethyl methacrylate) (P(GMA-HEMA)) brush-modified glass slides. After biotin is recognized with cyanine 3 (Cy3)-modified avidin (Cy3-avidin), the microarrays can produce strong fluorescence signal. The biotin moieties detach from microarray, when the biotin-modified peptide substrates are specially cleaved by a MMP, resulting in decreased fluorescence intensity of the microarray. The decreasing level of fluorescence intensity is correlated with the MMP inhibition. Nine known MMP inhibitors against MMP-2 and MMP-9 are evaluated by the assay, and the quantitative determination of inhibitory potencies (half maximal inhibitory concentration) are obtained, which are comparable with the literatures. Two biocompatible fluorogenic peptides containing MMP-specific recognition sequences and FAM/Dabcyl fluorophore-quencher pair are designed as activatable reporter probes for sensing MMP-2 and MMP-9 activities in cell and in vivo. The peptide microarray-based results are well verified by the cell inhibition assay and in vitro fluorescence imaging, and further confirmed by the in vivo imaging of HT-1080 tumor-bearing mice.

Polyacrylamide-phytic acid-polydopamine conducting porous hydrogel for rapid detection and removal of copper (II) ions.

In this work, a conducting porous polymer hydrogel-based electrochemical sensor has been developed for rapid detection of copper (II) ions (Cu2+). The polymer (termed as PAAM/PA/PDA) hydrogel is prepared through multi-interactions of the monomers dopamine (DA), acrylamide (AAM) and phytic acid (PA) under mild ambient conditions: the AAM polymerizes through free-radical polymerization, DA occurs poly coupling reaction, and PA crosslinks polydopamine (PDA) and polyacrylamide (PAAM) by hydrogen bonds. The three dimensional (3D) network nanostructured PAAM/PA/PDA hydrogel not only provides a large surface area for increasing the amount of immobilized molecules/ions, but also exhibits a good conductivity. The PAAM/PA/PDA hydrogel-based electrochemical sensor exhibits a low detection limit (1nmolL-1, S/N=3) and wide linear range (from 1nmolL-1 to 1µmolL-1) for Cu2+ detection in aqueous samples. Furthermore, the Cu2+ can be sensitively detected by the electrochemical sensor in different sample matrices, indicating that the electrochemical sensor could be used to monitor Cu2+ with reasonable assay performance in practical samples. The PAAM/PA/PDA hydrogel also exhibits a good capacity to remove Cu2+(231.36±4.70mgg-1), which is superior to those of other adsorption materials reported in the literature. The facile synthesized PAAM/PA/PDA hydrogel provides a novel and regenerable platform for monitoring and removing Cu2+ in real samples.

Surfactant-Free Aqueous Synthesis of Novel Ba2GdF7:Yb3+, Er3+@PEG Upconversion Nanoparticles for in Vivo Trimodality Imaging.

In this work, we developed the surfactant-free aqueous synthesis of novel polyethylene glycol (PEG) coated Ba2GdF7:Yb3+, Er3+ upconversion nanoparticles (named as, Ba2GdF7:Yb3+, Er3+@PEG UCNPs) for in vivo multimodality imaging including upconversion luminescence (UCL), X-ray computed tomography (CT), and T1-weighted magnetic resonance (MR). The as-prepared Ba2GdF7:Yb3+, Er3+@PEG UCNPs not only present bright UCL and reasonably high CT/MR enhancements but also exhibit excellent colloidal stability, inappreciable cytotoxicity, and negligible organ toxicity. In particular, the Ba2GdF7:Yb3+, Er3+@PEG UCNPs emit red UCL with high intensity in the tumor site after intravenous injection via the tail vein of a nude mouse. The Ba2GdF7:Yb3+, Er3+@PEG UCNPs as contrast agents exhibit high-performance for in vivo trimodality (UCL/CT/MR) imaging of a tumor during HepG2 tumor-bearing nude mouse experiments.

A Motion Interference-Insensitive Flexible Dry Electrode.

OBJECTIVE: A novel dry electrode is developed to improve the comfortability and the capability of alleviating motion interference by combining microneedles array (MNA) with flexible substrate. METHODS: Silicon MNA with sharp tips and limited height is fabricated and transferred on a flexible Polydimethylsiloxane (PDMS) substrate through bonding. Poly (3, 4-ethylenedioxythiophene) doped with poly (styrenesulfonate) (PEDOT/PSS) is coated on the surface of flexible MNA to form a conductive layer. RESULTS: Flexible dry electrode with 1.2 cm diameter is successfully fabricated. The mean impedance magnitudes (measured on skin) at 10 Hz are 61.2 ±31.3 kΩ·cm(2) for flexible dry electrode, while the values are 114.9 ±36.1 kΩ·cm(2) for wet electrode and 335.7 ±110.5 kΩ·cm(2) for flexible planar dry electrode, respectively. In the process of biopotential recording, the flexible dry electrode has the similar performance as that of wet electrode. It exhibits more stable recording stability than rigid dry electrode in the movement state. CONCLUSION: By integrating flexible PDMS substrate, sharp and hard MNA structure, as well as PEDOT/PSS coated surface together, a novel dry electrode is developed to meet the comfortable and antimotion interference requirement of wearable equipment. SIGNIFICANCE: The novel flexible dry electrode provides a simple and comfortable method to record biopotential signals in daily life.

Gram-scale synthesis of coordination polymer nanodots with renal clearance properties for cancer theranostic applications.

An ultrasmall hydrodynamic diameter is a critical factor for the renal clearance of nanoparticles from the body within a reasonable timescale. However, the integration of diagnostic and therapeutic components into a single ultrasmall nanoparticle remains challenging. In this study, pH-activated nanodots (termed Fe-CPNDs) composed of coordination polymers were synthesized via a simple and scalable method based on coordination reactions among Fe(3+), gallic acid and poly(vinylpyrrolidone) at ambient conditions. The Fe-CPNDs exhibited ultrasmall (5.3 nm) hydrodynamic diameters and electrically neutral surfaces. The Fe-CPNDs also exhibited pH-activatable magnetic resonance imaging contrast and outstanding photothermal performance. The features of Fe-CPNDs greatly increased the tumour-imaging sensitivity and facilitated renal clearance after injection in animal models in vivo. Magnetic resonance imaging-guided photothermal therapy using Fe-CPNDs completely suppressed tumour growth. These findings demonstrate that Fe-CPNDs constitute a new class of renal clearable nanomedicine for photothermal therapy and molecular imaging.

Effects of subretinal implant materials on the viability, apoptosis and barrier function of cultured RPE cells.

BACKGROUND: Subretinal microphotodiode array (MPDA) is a type of visual prosthesis used for the implantation in the subretinal space of patients with progressive photoreceptor cell loss. The present study aimed to evaluate the effect of materials for MPDA on the viability, apoptosis and barrier function of cultured pig retinal pigment epithelium (RPE) cells. METHODS: Primary culture of pig RPE cells was performed and 24 pig eyes were used to start RPE culture. The third passage of the cultures was plated on different materials for MPDA and MPDAs. The tetrazolium dye-reduction assay (MTT) was used to determine RPE cell viability. Flow cytometry was measured to indicate the apoptosis rates of RPE cells on different materials. RPE cells were also cultured on microporous filters, and the transepithelial resistance and permeability of the experimental molecule were measured to determine the barrier function. RESULTS: The data from all the methods indicated no significant difference between the materials groups and the control group, and the materials tested showed good biocompatibility. CONCLUSIONS: The materials for MPDA used in the present study had no direct toxicity to the RPE cells and did not release harmful soluble factors that affected the barrier function of RPE in vitro.