9 research outputs found
Bioinspired aryldiazonium carbohydrate coatings: reduced adhesion of foulants at polymer and stainless steel surfaces in a marine environment
Surface treatments that minimize biofouling in marine environments are of interest for a variety of applications such as environmental monitoring and aquaculture. We report on the effect of saccharide coatings on biomass accumulation at the surface of three materials that find applications in marine settings: stainless steel 316 (SS316), Nylon-6 (N-6), and poly(ether sulfone) (PES). Saccharides were immobilized via aryldiazonium chemistry; SS316 and N-6 samples were subjected to oxidative surface pretreatments prior to saccharide immobilization, whereas PES was modified via direct reaction of pristine surfaces with the aryldiazonium cations. Functionalization was confirmed by a combination of X-ray photoelectron spectroscopy, contact angle experiments, and fluorescence imaging of lectin–saccharide binding. Saccharide immobilization was found to increase surface hydrophilicity of all materials tested, while laboratory tests demonstrate that the saccharide coating results in reduced protein adsorption in the absence of specific protein–saccharide interactions. The performance of all three materials after modification with aryldiazonium saccharide films was tested in the field via immersion of modified coupons in coastal waters over a 20 day time period. Results from combined infrared spectroscopy, light microscopy, scanning electron and He-ion microscopy, and adenosine-triphosphate content assays show that the density of retained biomass at surfaces is significantly lower on carbohydrate modified samples with respect to unmodified controls. Therefore, functionalization and field test results suggest that carbohydrate aryldiazonium layers could find applications as fouling resistant coatings in marine environments
Phospholipid film in electrolyte-gated organic field-effect transistors
A totally innovative electrolyte-gated field effect transistor, embedding a phospholipid film at the interface between the organic semiconductor and the gating solution, is described. The electronic properties of OFETs including a phospholipid film are studied in both pure water and in an electrolyte solution and compared to those of an OFET with the organic semiconductor directly in contact with the gating solution. In addition, to investigate the role of the lipid layers in the charge polarization process and quantify the field-effect mobility, impedance spectroscopy was employed. The results indicate that the integration of the biological film minimizes the penetration of ions into the organic semiconductor thus leading to a capacitive operational mode as opposed to an electrochemical one. The OFETs operate at low voltages with a field-effect mobility in the 10−3 cm2 V−1 s−1 range and an on/off current ratio of 103. This achievement opens perspectives to the development of FET biosensors potentially capable to operate in direct contact with physiological fluids.funding agencies|European Union|248728
Phospholipid film in electrolyte-gated organic field-effect transistors
A totally innovative electrolyte-gated field effect transistor, embedding a phospholipid film at the interface between the organic semiconductor and the gating solution, is described. The electronic properties of OFETs including a phospholipid film are studied in both pure water and in an electrolyte solution and compared to those of an OFET with the organic semiconductor directly in contact with the gating solution. In addition, to investigate the role of the lipid layers in the charge polarization process and quantify the field-effect mobility, impedance spectroscopy was employed. The results indicate that the integration of the biological film minimizes the penetration of ions into the organic semiconductor thus leading to a capacitive operational mode as opposed to an electrochemical one. The OFETs operate at low voltages with a field-effect mobility in the 10−3 cm2 V−1 s−1 range and an on/off current ratio of 103. This achievement opens perspectives to the development of FET biosensors potentially capable to operate in direct contact with physiological fluids.funding agencies|European Union|248728
Carbohydrate Coatings via Aryldiazonium Chemistry for Surface Biomimicry
Carbohydrates are extremely important
biomolecules and their immobilization
onto solid surfaces is of interest for the development of new biomimetic
materials and of new methods for understanding processes in glycobiology.
We have developed an efficient surface modification methodology for
the functionalization of a range of materials with biologically active
carbohydrates based on aryldiazonium chemistry. We describe the synthesis
and characterization of carbohydrate reagents, which were subsequently
employed for the one-step, solution-based modification of carbon,
metals, and alloys with monosaccharides. We used a combination of
spectroscopic and nanogravimetric methods to characterize the structure
of the carbohydrate layers; we report an average surface coverage
of 7.8 × 10<sup>–10</sup> mol cm<sup>–2</sup> under
our experimental conditions. Concanavalin A, a mannose-binding lectin,
and Peanut Agglutinin, a galactose-binding lectin, were found to bind
from solution to their respective monosaccharide binding partners
immobilized at the surface. This result suggests that the spontaneous
chemisorption of aryldiazonium monosaccharide precursors leads to
the formation of monosaccharide layers that retain the biological
recognition specificity of the parent carbohydrate molecule. Finally,
we carried out measurements using fluorescently labeled Bovine Serum
Albumin (BSA) and found that these carbohydrate coatings reduce unspecific
adsorption of this protein at carbon surfaces. These results suggest
that aryldiazonium-derived carbohydrate coatings may offer a promising
strategy for preventing undesirable protein accumulation onto surfaces
Enhanced Antifouling Properties of Carbohydrate Coated Poly(ether sulfone) Membranes
PolyÂ(ether sulfone) membranes (PES)
were modified with biologically
active monosaccharides and disaccharides using aryldiazonium chemistry
as a mild, one-step, surface-modification strategy. We previously
proposed the modification of carbon, metals, and alloys with monosaccharides
using the same method; herein, we demonstrate modification of PES
membranes and the effect of chemisorbed carbohydrate layers on their
resistance to biofouling. Glycosylated PES surfaces were characterized
using spectroscopic methods and tested against their ability to interact
with specific carbohydrate-binding proteins. Galactose-, mannose-,
and lactose-modified PES surfaces were exposed to Bovine Serum Albumin
(BSA) solutions to assess unspecific protein adsorption in the laboratory
and were found to adsorb significantly lower amounts of BSA compared
to bare membranes. The ability of molecular carbohydrate layers to
impart antifouling properties was further tested in the field via
long-term immersive tests at a wastewater treatment plant. A combination
of ATP content assays, infrared spectroscopic characterization and
He-ion microscopy (HIM) imaging were used to investigate biomass accumulation
at membranes. We show that, beyond laboratory applications and in
the case of complex aqueous environments that are rich in biomass
such as wastewater effluent, we observe significantly lower biofouling
at carbohydrate-modified PES than at bare PES membrane surfaces
Electronic transduction of proton translocations in nanoassembled lamellae of bacteriorhodopsin
An organic field-effect transistor (OFET) integrating bacteriorhodopsin (bR) nanoassembled lamellae is proposed for an in-depth study of the proton translocation processes occurring as the bioelectronic device is exposed either to light or to low concentrations of general anesthetic vapors. The study involves the morphological, structural, electrical, and spectroscopic characterizations necessary to assess the functional properties of the device as well as the bR biological activity once integrated into the functional biointerlayer (FBI)-OFET structure. The electronic transduction of the protons phototranslocation is shown as a current increase in the p-type channel only when the device is irradiated with photons known to trigger the bR photocycle, while Raman spectroscopy reveals an associated C=C isomer switch. Notably, higher energy photons bring the cis isomer back to its trans form, switching the proton pumping process off. The investigation is extended also to the study of a PM FBI-OFET exposed to volatile general anesthetics such as halothane. In this case an electronic current increase is seen upon exposure to low, clinically relevant, concentrations of anesthetics, while no evidence of isomer-switching is observed. The study of the direct electronic detection of the two different externally triggered proton translocation effects allows gathering insights into the underpinning of different bR molecular switching processes. © 2014 American Chemical Society