Impact of Poly(dimethylsiloxane) Surface Modification with Conventional and Amino Acid-Conjugated Self-Assembled Monolayers on the Differentiation of Induced Pluripotent Stem Cells into Cardiomyocytes.

Cardiomyocytes, differentiated from induced pluripotent stem cells (iPSCs), have the potential to produce patient- and disease-specific pharmacological and toxicological platforms, in addition to their cardiac cell therapy applications. However, the lack of both a robust and a simple procedure for scalable cell substrate production is one of the major limitations in this area. Mimicking the natural healthy myocardium extracellular matrix (ECM) properties by altering the cell substrate properties, such as stiffness and chemical/biochemical composition, can significantly affect cell substrate interfacial characteristics and potentially influence cellular behavior and differentiation of iPSCs to cardiomyocytes. Here, we propose a systematic and biomimetic approach, based on the preparation of poly(dimethylsiloxane) (PDMS) substrates having the similar stiffness as healthy heart tissue and a well-defined surface chemistry obtained by conventional [(3-aminopropyl)triethoxysilane (APTES) and octadecyltrimethoxysilane (OTS)] and amino acid (histidine and leucine)-conjugated self-assembled monolayers (SAMs). Among a wide range of different concentrations, the 50:1 prepolymer cross-linker ratio of PDMS allowed adaptation of the myocardium stiffness with a Young's modulus of 23.79 ± 0.61 kPa. Compared with conventional SAM modification, amino acid-conjugated SAMs greatly improved iPSC adhesion, viability, and cardiac marker expression by increasing surface biomimetic properties, whereas all SAMs enhanced cell behavior, with respect to native PDMS. Furthermore, leucine-conjugated SAM modification provided the best environment for cardiac differentiation of iPSCs. This optimized approach can be easily adapted for cardiac differentiation of iPSCs in vitro, rendering a very promising tool for microfluidics, drug screening, and organ-on-chip platforms.

A facile surface modification of poly(dimethylsiloxane) with amino acid conjugated self-assembled monolayers for enhanced osteoblast cell behavior.

Polydimethylsiloxane (PDMS) is a biocompatible synthetic polymer and used in various applications due to its low toxicity and tunable surface properties. However, PDMS does not have any chemical cues for cell binding. Plasma treatment, protein coating or surface modification with various molecules have been used to improve its surface characteristics. Still, these techniques are either last for a very limited time or have very complicated experimental procedures. In the present study, simple and one-step surface modification of PDMS is successfully accomplished by the preparation of hydrophilic and hydrophobic amino acid conjugated self-assembled monolayers (SAMs) for enhanced interactions at the cell-substrate interface. Synthesis of histidine and leucine conjugated (3-aminopropyl)-triethoxysilane (His-APTES and Leu-APTES) were confirmed with proton nuclear magnetic resonance spectroscopy (1H NMR) and optimum conditions for the modification of PDMS with SAMs were investigated by X-ray photoelectron spectroscopy (XPS) analysis, combined with water contact angle (WCA) measurements. Results indicated that both SAMs enhanced cellular behavior in vitro. Furthermore, hydrophilic His-APTES modification provides a superior environment for the osteoblast maturation with higher alkaline phosphatase activity and mineralization. As histidine, leucine, and functional groups of these SAMs are naturally found in biological systems, modification of PDMS with them increases its cell-substrate surface biomimetic properties. This study establishes a successful modification of PDMS for in vitro cell studies, offering a biomimetic and easy procedure for potential applications in microfluidics, cell-based therapies, or drug investigations.

3D Micropatterned All-Flexible Microfluidic Platform for Microwave-Assisted Flow Organic Synthesis.

A large-area, all-flexible, microwaveable polydimethoxysilane microfluidic reactor was fabricated by using a 3D printing system. The sacrificial microchannels were printed on polydimethoxysilane substrates by a direct ink writing method using water-soluble Pluronic F-127 ink and then encapsulated between polydimethoxysilane layers. The structure of micron-sized channels was analyzed by optical and electron microscopy techniques. The fabricated flexible microfluidic reactors were utilized for the acetylation of different amines under microwave irradiation to obtain acetamides in shorter reaction times and good yields by flow organic synthesis.

Does Para-chloroaniline Really Form after Mixing Sodium Hypochlorite and Chlorhexidine?

INTRODUCTION: Mixing sodium hypochlorite (NaOCl) with chlorhexidine (CHX) forms a brown-colored precipitate. Previous studies are not in agreement whether this precipitate contains para-chloroaniline (PCA). Tests used for analysis may demonstrate different outcomes. Purpose of this study was to determine whether PCA is formed through the reaction of mixing NaOCl and CHX by using high performance liquid chromatography, proton nuclear magnetic resonance spectroscopy, gas chromatography, thin layer chromatography, infrared spectroscopy, and gas chromatography/mass spectrometry. METHODS: To obtain a brown precipitate, 4.99% NaOCl was mixed with 2.0% CHX. This brown precipitate was analyzed and compared with signals obtained from commercially available 4.99% NaOCl, 2% solutions, and 98% PCA in powder form. RESULTS: Chromatographic and spectroscopic analyses showed that brown precipitate does not contain free PCA. CONCLUSIONS: This study will be a cutoff proof for the argument on PCA formation from reaction of CHX and NaOCl.

Developing column material for the separation of serum amyloid P and C reactive protein from biological sources.

In this study, we have investigated the isolation of serum amyloid P (SAP) and C-reactive protein (CRP) from rainbow trout. It has recently been found that SAP is deposited in atherosclerotic lesions or neurofibrillary tangles, which are related to aging process and Alzheimer's disease. Given the importance of CRP, the CRP level in blood is becoming recognized as a potential means of monitoring cardiovascular risk. These two proteins, members of the pentraxin family of oligomeric serum proteins, were isolated from rainbow trout using N-methacryloyl-phosphoserine (MA-pSer) immobilized poly (2-hydroxy ethylmethacrylate) (PHEMA) cryogels as a column material in a fast protein liquid chromatography system. The separation process was verified in two steps. First, SAP and CRP proteins were isolated together from serum sample of rainbow trout using MA-pSer/PHEMA cryogel columns. Second, SAP protein was separated chromatographically from CRP protein using the Ca(2+) ion immobilized PHEMA cryogel column. According to the data, a new and effective technique has been developed for the isolation of SAP and CRP proteins from a biological source, rainbow trout. Finally, purified SAP and CRP were loaded using sodium dodecyl sulfate-polyacrylamide gel and western blot analysis to investigate the purity of chromatographically isolated SAP and CRP compared with commertial SAP and CRP.

Bitargeting and ambushing nanotheranostics.

The main problem in cancer chemotherapy is the cytotoxic side effects of therapeutics on healthy tissues and cells. The targeted drug delivery and nanotechnology are intensively investigated area to find new ways to solve, at least to reduce, these problems. Hereby, we have reported a new method inspired from both conventional military strategies and biorecognition in the body. In this respect, we have produced two fluorescent nano-drug systems with bitargeting and biorecognition properties, recognizing cancer cells and each other. The multiplexed nanostructures were interacted with HL-60 cells to show their efficiency for bitargeting, ambushing, timed, and double-controlled cancer cell apoptosis.

New synthesis method for 4-MAPBA monomer and using for the recognition of IgM and mannose with MIP-based QCM sensors.

Quartz crystal microbalance (QCM) sensors coated with molecularly imprinted polymers (MIP) have been developed for the recognition of immunoglobulin M (IgM) and mannose. In this method, methacryloylamidophenylboronic acid (MAPBA) was used as a monomer and mannose was used as a template. For this purpose, initially, QCM electrodes were modified with 2-propene-1-thiol to form mannose-binding regions on the QCM sensor surface. In the second step, the methacryloylamidophenylboronic acid-mannose [MAPBA-mannose], pre-organized monomer system, was prepared using the MAPBA monomer. Then, a molecularly imprinted film was coated on to the QCM electrode surface under UV light using ethylene glycol dimethacrylate (EDMA), and azobisisobutyronitrile (AIBN) as a cross-linking agent and an initiator, respectively. The mannose can be simultaneously bound to MAPBA and fitted into the shape-selective cavities. The binding affinity of the mannose-imprinted sensors was investigated using the Langmuir isotherm. The mannose-imprinted QCM electrodes have shown homogeneous binding sites for mannose (K(a): 3.3 × 10(4) M(-1)) and heterogeneous binding sites for IgM (K(a1): 1.0 × 10(4) M(-1); K(a2): 3.3 × 10(3) M(-1)).

4-Aminophenyl boronic acid modified gold platforms for influenza diagnosis.

As a potential pandemic threat to human health, there has been an urgent need for rapid, sensitive, simpler and less expensive detection method for the highly pathogenic influenza A virus. For this purpose, Quartz Crystal Microbalance (QCM) and Surface Plasmon Resonance (SPR) sensors have been developed for the recognition of hemagglutinin (HA) which is a major protein of influenza A virus. 4-Aminophenyl boronic acid (4-APBA) has been synthesized and used as a new ligand for binding of sialic acid (SA) via boronic acid-sugar interaction. SA has an important role in binding of HA. QCM and SPR sensor surfaces have been modified with thiol groups and then 4-APBA and SA have been immobilized on sensor surfaces, respectively. Sensor surfaces have been screened with AFM and used for the determination of HA from aqueous solution. The selective recognition of the QCM and SPR sensors toward Concanavalin A has been reported in this work. Also, the binding capacity and detection limits of QCM and SPR sensors have been calculated and detection limits were found to be 4.7 × 10(-2) µM, (0.26 µg ml(-1)) and 1.28 × 10(-1) µM, (0.72 µg ml(-1)) in the 95% confidence interval, respectively.

Bioconjugated and cross-linked bionanostructures for bifunctional immunohistochemical labeling.

The present study describes the development and use of a new bioconjugate combining targeted quantum dot labeling with an immunoperoxidase method and explores whether these bioconjugates could specifically and effectively label Cu/Zn superoxide dismutase (SOD1). The new bioconjugate is designed for the examination of samples both under fluorescent and bright-field microscopy at the same time. For this purpose chlorobis(2-2'-bipyridyl) methacryloyl tyrosine-ruthenium(II) and bis (2-2'-bipyridyl) methacryloyltyrosine-methacryloyltryptophan-ruthenium (II) photosensitive monomers and photosensitive poly(Bis (2-2'-bipyridyl)) methacryloyltyrosine-methacryloyltryptophan-ruthenium(II) were synthesized and characterized. The anti-SOD1 antibody and horseradish peroxidase (HRD) conjugated quantum dots were prepared by using this polymer. The anti-SOD1 antibody and HRD conjugated quantum dots were used in labeling and imaging of SOD1 in rat liver sections. Quantum dot particles were observed as a bright fluorescence in their specific binding locations inside the hepatocytes. The HRD-diaminobenzidine reaction product was observed as brown-colored particles at the same locations under bright-field microscopy. Structural details of the tissue sections could be examined at the same time. The conjugation protocol is simple; the bioconjugate is applicable for efficient cell labeling and can be adapted for imaging of other targets in different tissues. Also, the prepared nanobioconjugates have mechanic stability and can be used for a long period.

Mutual recognition of TNT using antibodies polymeric shell having CdS.

Click chemistry is the latest strategy called upon in the development of state of the art exponents of bioconjugation. In this study, we have proposed a covalent and photosensitive crosslinking conjugation of the antibody on nano-structures. For this purpose, quantum dots (QDs) without affecting conformation and function of proteins through the ruthenium-chelate based aminoacid monomer linkages have been applied. The aminoacid-monomer linkages called ANADOLUCA (AmiNoAcid Decorated and Light Underpining Conjugation Approach) give reusable oriented and cross-linked anti 2,4,6-trinitrotoluene (TNT) conjugated QD for TNT detection. In this work, a new and simple method has improved to design and prepare high sensitive nanoconjugates for TNT determination. We have demonstrated the use of luminescent QDs conjugated to antibody for the specific detection of the explosive TNT in aqueous environments. The binding affinity of each nanoconjugates for TNT detection by using Langmuir adsorption methods has also been investigated.

Interaction of cancer cells with magnetic nanoparticles modified by methacrylamido-folic acid.

BACKGROUND: Magnetic nanoparticles show great promise for use as tools in a wide variety of biomedical applications. The purpose of this study was to investigate the potential effects of methacrylamido-folic acid (Ma-Fol)-modified magnetic nanoparticles on 5RP7 (H-ras-transformed rat embryonic fibroblasts) and NIH/3T3 (normal mouse embryonic fibroblasts). METHODS: The cytotoxicity and viability of 5RP7 and NIH/3T3 cells were detected. The percentage of cells undergoing apoptosis was analyzed by flow cytometry using Annexin V-fluorescein isothiocyanate staining. Nanoparticle internalization into 5RP7 and NIH/3T3 cells was visualized by transmission electron microscopy. CONCLUSION: In this study, folic acid coupled to the surface of iron oxide for selective binding to cancer cells and immobilized the surfaces of magnetic nanoparticles. This complex improves cell internalization and targeting of cancer cells. We detected increased apoptosis using flow cytometry and transmission electron microscopy. RESULTS: Folic acid modification of magnetic nanoparticles could be used to facilitate uptake to specific cancer cells for cancer therapy and diagnosis. Our results showed that the uptake of folic-acid modified nanoparticles by 5RP7 cancer cells was also much higher than that of 3T3 cells. This modification can be used for successful targeting of cancer cells expressing the folate receptor.

Investigation of photosensitively bioconjugated targeted quantum dots for the labeling of Cu/Zn superoxide dismutase in fixed cells and tissue sections.

This study presents the development of targeted and antibody cross-linked QDs and explores whether these bioconjugates could specifically and effectively label Cu/Zn superoxide dismutase (SOD1) on fixed cells and tissues. QD-antibody conjugation was achieved by using our previously invented AmiNoacid (monomer) Decorated and Light Underpining Conjugation Approach (ANADOLUCA) method. In this method, we have used a photosensitive aminoacid monomer having ruthenium complex which is a synthetic and inexpensive material for the preparation of bioconjugates. Its specificity was demonstrated by extracting the active enzyme from rat liver lysate by using the bioconjugate. It provided accurate antibody orientation, high specificity and mechanic stability. The protocol steps for QD-antibody conjugation and specimen preparation were described in detail. The nanobioconjugates were prepared under mild conditions (for example in day light), independent of pH and temperature, without affecting conformation and function of protein. This protocol is simple, inexpensive and can be successfully adapted to detect other targets on different cell types and tissues.

Quantum dot nanocrystals having guanosine imprinted nanoshell for DNA recognition.

Molecular imprinted polymers (MIPs) as a recognition element for sensors are increasingly of interest and MIP nanoparticles have started to appear in the literature. In this study, we have proposed a novel thiol ligand-capping method with polymerizable methacryloylamido-cysteine (MAC) attached to CdS quantum dots (QDs), reminiscent of a self-assembled monolayer and have reconstructed surface shell by synthetic host polymers based on molecular imprinting method for DNA recognition. In this method, methacryloylamidohistidine-platinium (MAH-Pt(II)) is used as a new metal-chelating monomer via metal coordination-chelation interactions and guanosine templates of DNA. Nanoshell sensors with guanosine templates give a cavity that is selective for guanosine and its analogues. The guanosine can simultaneously chelate to Pt(II) metal ion and fit into the shape-selective cavity. Thus, the interaction between Pt(II) ion and free coordination spheres has an effect on the binding ability of the CdS QD nanosensor. The binding affinity of the guanosine imprinted nanocrystals has investigated by using the Langmuir and Scatchard methods, and experiments have shown the shape-selective cavity formation with O6 and N7 of a guanosine nucleotide (K(a) = 4.841x10(6) mol L(-1)) and a free guanine base (K(a) = 0.894x10(6) mol L(-1)). Additionally, the guanosine template of the nanocrystals is more favored for single stranded DNA compared to double stranded DNA.

A spectroelectrochemical study on single-oscillator model and optical constants of sulfonated polyaniline film.

The optical properties of sulfonated polyaniline (SPAN) thin film prepared by electrochemical method have been investigated. Polychromic behavior of SPAN thin film (transparent yellow-green-dark blue) was observed when the cyclic voltammograms were taken between -0.25 V and +1.90 V (vs. Ag/AgCl, sat.) during the growth of polyaniline film. In situ UV-vis spectra of the polymers-indium tin oxide (ITO) glass electrode were taken during the oxidation of the polymers at different applied potentials. The direct band gap values of SPAN thin film changed from 3.771 eV to 3.874 eV with the applied potentials. From in situ UV-vis spectra, the optical constants such as refractive index and dielectric constant of the SPAN thin film were determined. The important changes in absorption edge, refractive index and the dielectric constant were observed due to the applied potentials. The refractive index dispersion curves of the film obey the single-oscillator model and oscillator parameters changed with the applied potentials. The most significant result of the present work is in situ spectroelectrochemical method, which can be used to modify the optical band gaps and constants.