The Effect of Physical and Chemical Cues on Hepatocellular Function and Morphology

Physical topographical features and/or chemical stimuli to the extracellular matrix (ECM) provide essential cues that manipulate cell functions. From the physical point of view, contoured nanostructures are very important for cell behavior in general, and for cellular functions. From the chemical point of view, ECM proteins containing an RGD sequence are known to alter cell functions. In this study, the influence of integrated physical and chemical cues on a liver cell line (HepG2) was investigated. To mimic the physical cues provided by the ECM, amorphous TiO2 nanogratings with specific dimensional and geometrical characteristics (nanogratings 90 nm wide and 150 nm apart) were fabricated. To mimic the chemical cues provided by the ECM, the TiO2 inorganic film was modified by immobilization of the RGD motif. The hepatic cell line morphological and functional changes induced by simultaneously combining these diversified cues were investigated, including cellular alignment and the expression of different functional proteins. The combination of nanopatterns and surface modification with RGD induced cellular alignment and expression of functional proteins, indicating that physical and chemical cues are important factors for optimizing hepatocyte function

Characterization of Hexenuronosyl Xylan-degrading Enzymes Produced by Paenibacillus sp. 07

The enzyme involved in hexenuronic acid (HexA) removal from kraft pulp was identified in Paenibacillus sp. strain 07. Extracellular and intracellular enzymes of Paenibacillus sp. were assessed for their hexenuronosyl-xylotriose (∆X3) degradation activity. First, ∆X3 was obtained from hardwood kraft pulp by enzymatic hydrolysis using three commercial enzymes. Crude extracellular and intracellular enzyme fractions were obtained from Paenibacillus cultures cultivated in 0.5% (w/v) birch wood xylan as the sole carbon source. The ∆X3-degrading activities of the enzyme fractions were measured by hydrolysis assays in sodium acetate buffer containing ∆X3 substrate (pH 6) at 50 °C. The reaction products were analyzed by high-performance anion-exchange chromatography with pulsed amperometric detection. The enzyme fractions displayed different chromatogram patterns. After treatment with the intracellular enzyme fraction, the chromatograms displayed xylose and hexenuronosyl xylobiose (∆X2) peaks. The chromatogram patterns of the extracellular fraction assays indicated xylose, xylotriose, and ∆X2 production. Thus, the intracellular enzymes of Paenibacillus can hydrolyze the xylosidic linkages at the reducing ends of ∆X3, whereas a specific extracellular enzyme can hydrolyze HexA. This enzyme is potentially applicable to HexA removal during bio-bleaching

Nanostructures Control the Hepatocellular Responses to a Cytotoxic Agent “Cisplatin”

In drug discovery programs, the alteration between in vivo and in vitro cellular responses to drug represents one of the main challenges. Since the variation in the native extracellular matrix (ECM) between in vivo and 2D in vitro conditions is one of the key reasons for such discrepancies, thus the utilization of substrate that likely mimics ECM characteristics (topography, stiffness, and chemical composition) is needed to overcome such problem. Here, we investigated the role of substrate nanotopography as one of the major determinants of hepatic cellular responses to a chemotherapeutic agent “cisplatin.” We studied the substratum induced variations in cisplatin cytotoxicity; a higher cytotoxic response to cisplatin was observed for cells cultured on the nanopattern relative to a flat substrate. Moreover, the nanofeatures with grating shapes that mimic the topography of major ECM protein constituents (collagen) induced alterations in the cellular orientation and chromatin condensation compared to flat surfaces. Accordingly, the developments of biomimetic substrates with a particular topography could have potentials in drug development analyses to reflect more physiological mimicry conditions in vitro

Metamaterial-enhanced vibrational absorption spectroscopy for the detection of protein molecules

From visible to mid-infrared frequencies, molecular sensing has been a major successful application of plasmonics because of the enormous enhancement of the surface electromagnetic nearfield associated with the induced collective motion of surface free carriers excited by the probe light. However, in the lower-energy terahertz (THz) region, sensing by detecting molecular vibrations is still challenging because of low sensitivity, complicated spectral features, and relatively little accumulated knowledge of molecules. Here, we report the use of a micron-scale thin-slab metamaterial (MM) architecture, which functions as an amplifier for enhancing the absorption signal of the THz vibration of an ultrathin adsorbed layer of large organic molecules. We examined bovine serum albumin (BSA) as a prototype large protein molecule and Rhodamine 6G (Rh6G) and 3,3'-diethylthiatricarbocyanine iodide (DTTCI) as examples of small molecules. Among them, our MM significantly magnified only the signal strength of bulky BSA. On the other hand, DTTCI and Rh6G are inactive, as they lack low-frequency vibrational modes in this frequency region. The results obtained here clearly demonstrate the promise of MM-enhanced absorption spectroscopy in the THz region for detection and structural monitoring of large biomolecules such as proteins or pathogenic enzymes

Dark-Field Scattering and Local SERS Mapping from Plasmonic Aluminum Bowtie Antenna Array

On the search for the practical plasmonic materials beyond noble metals, aluminum has been emerging as a favorable candidate as it is abundant and offers the possibility of tailoring the plasmonic resonance spanning from ultra-violet to the infrared range. In this letter, in combination with the numerical electromagnetic simulations, we experimentally study the dark-field scattering spectral mapping of plasmonic resonance from the free-standing Al bowtie antenna arrays and correlate their strong nearfield enhancement with the sensing capability by means of surface-enhanced Raman spectroscopy. The spatial matching of plasmonic and Raman mapping puts another step to realize a very promising application of free-standing Al bowtie antennas for plasmonic sensing