Antifouling Polymer Brushes Displaying Antithrombogenic Surface Properties.

The contact of blood with artificial materials generally leads to immediate protein adsorption (fouling), which mediates subsequent biological processes such as platelet adhesion and activation leading to thrombosis. Recent progress in the preparation of surfaces able to prevent protein fouling offers a potential avenue to mitigate this undesirable effect. In the present contribution, we have prepared several types of state-of-the-art antifouling polymer brushes on polycarbonate plastic substrate, and investigated their ability to prevent platelet adhesion and thrombus formation under dynamic flow conditions using human blood.

Utilizing a Key Aptamer Structure-Switching Mechanism for the Ultrahigh Frequency Detection of Cocaine.

Aptasensing of small molecules remains a challenge as detection often requires the use of labels or signal amplification methodologies, resulting in both difficult-to-prepare sensor platforms and multistep, complex assays. Furthermore, many aptasensors rely on the binding mechanism or structural changes associated with target capture by the aptameric probe, resulting in a detection scheme customized to each aptamer. It is in this context that we report herein a sensitive cocaine aptasensor that offers both real-time and label-free measurement capabilities.

Prevention of surface-induced thrombogenesis on poly(vinyl chloride).

Much biomedical equipment consisting of or containing plastic polymer(s) must come into contact with blood - an interaction that, at the molecular level, may unfortunately prompt biological processes with potentially deleterious, short- or long-term effects such as thrombosis. In the present investigation, this problem is alleviated for poly(vinyl chloride) (PVC) through chemical surface modification with an ultrathin, monoethylene glycol-based coating - a transformation that is characterized using X-ray photoelectron spectroscopy (XPS) supplemented by contact angle goniometry (CAG). Antithrombogenic properties are assessed through calculation (for the first 10 min, and after 60 min) of the surface coverage percentage due to platelet adhesion, aggregation and thrombus formation upon continuous exposure to fluorescently-labelled whole human blood.

A survey of state-of-the-art surface chemistries to minimize fouling from human and animal biofluids.

Upon contact with bodily fluids, synthetic materials spontaneously acquire a layer of various species (most notably proteins) on their surface. The concern with respect to biomedical equipment, implants or devices resides in the possibility for biological processes with potentially harmful effects to ensue. In biosensor technology, the issue with this natural fouling phenomenon is that of non-specific adsorption to sensing platforms, which generates an often overwhelming interference signal that prevents the detection, not to mention the quantification, of target analytes present at considerably lower concentration.

Ultrathin Surface Chemistry to Delay Anion Fouling.

The unwanted fouling of surfaces by ionic adsorption has received little research attention. In this context, ultrathin organic adlayer surface chemistry-featuring monoethylene glycol based molecular residues-is described that is capable of noticeably decreasing the rate of anion depletion from solution. The strategy is exemplified with glass as the substrate material and fluoride as the anion foulant.

Ultra-high frequency piezoelectric aptasensor for the label-free detection of cocaine.

This paper describes a label-free and real-time piezoelectric aptasensor for the detection of cocaine. The acoustic wave sensing platform is a quartz substrate functionalized with an adlayer of S-(11-trichlorosilyl-undecanyl)-benzenethiosulfonate (BTS) cross-linker onto which the anti-cocaine MN4 DNA aptamer is next immobilized. Preparation of the sensor surface was monitored using X-ray photoelectron spectroscopy (XPS), while the binding of cocaine to surface-attached MN4 was evaluated using the electromagnetic piezoelectric acoustic sensor (EMPAS).

Adlayer-mediated antibody immobilization to stainless steel for potential application to endothelial progenitor cell capture.

This work describes the straightforward surface modification of 316L stainless steel with BTS, S-(11-trichlorosilylundecanyl)-benzenethiosulfonate, a thiol-reactive trichlorosilane cross-linker molecule designed to form intermediary coatings with subsequent biofunctionalization capability. The strategy is more specifically exemplified with the immobilization of intact antibodies and their Fab' fragments. Both surface derivatization steps are thoroughly characterized by means of X-ray photoelectron spectroscopy.

On the hydration of subnanometric antifouling organosilane adlayers: a molecular dynamics simulation.

The connection between antifouling and surface hydration is a fascinating but daunting question to answer. Herein, we use molecular dynamics (MD) computer simulations to gain further insight into the role of surface functionalities in the molecular-level structuration of water (surface kosmotropicity)--within and atop subnanometric organosilane adlayers that were shown in previous experimental work to display varied antifouling behavior. Our simulations support the hypothesized intimate link between surface hydration and antifouling, in particular the importance of both internal and interfacial hydrophilicity and kosmotropicity.

A true theranostic approach to medicine: towards tandem sensor detection and removal of endotoxin in blood.

Sepsis is one of the leading causes of death around the world. The condition occurs when a local infection overcomes the host natural defense mechanism and suddenly spreads into the circulatory system, triggering a vigorous, self-injurious inflammatory host response. The pathogenesis of sepsis is relatively well known, one of the most potent immuno-activator being bacterial lipopolysaccharide (LPS) - also known as 'endotoxin'.

Prevention of thrombogenesis from whole human blood on plastic polymer by ultrathin monoethylene glycol silane adlayer.

In contemporary society, a large percentage of medical equipment coming in contact with blood is manufactured from plastic polymers. Unfortunately, exposure may result in undesirable protein-material interactions that can potentially trigger deleterious biological processes such as thrombosis. To address this problem, we have developed an ultrathin antithrombogenic coating based on monoethylene glycol silane surface chemistry.

Probing the hydration of ultrathin antifouling organosilane adlayers using neutron reflectometry.

Neutron reflectometry data and modeling support the existence of a relatively thick, continuous phase of water stemming from within an antifouling monoethylene glycol silane adlayer prepared on oxidized silicon wafers. In contrast, this physically distinct (from bulk) interphase is much thinner and only interfacial in nature for the less effective adlayer lacking internal ether oxygen atoms. These results provide further insight into the link between antifouling and surface hydration.

Critical role of surface hydration on the dynamics of serum adsorption studied with monoethylene glycol adlayers on gold.

The dynamics of serum adsorption on bare and monoethylene glycol adlayer-modified gold surfaces is investigated using acoustic wave physics. Hydration experiments support the pivotal role ascribed to water in the antifouling of surfaces. Behavioural discrepancy is interpreted in terms of difference in water structuring properties (surface kosmotropicity).

Surface chemistry to minimize fouling from blood-based fluids.

Upon contact with bodily fluids/tissues, exogenous materials spontaneously develop a layer of proteins on their surface. In the case of biomedical implants and equipment, biological processes with deleterious effects may ensue. For biosensing platforms, it is synonymous with an overwhelming background signal that prevents the detection/quantification of target analytes present in considerably lower concentrations.

New functionalizable alkyltrichlorosilane surface modifiers for biosensor and biomedical applications.

We report herein three unprecedented alkyltrichlorosilane surface modifiers bearing pentafluorophenyl ester (PFP), benzothiosulfonate (BTS), or novel β-propiolactone (BPL) functionalizable terminal groups. Evidence is provided that these molecules can be prepared in very high purity (as assessed by NMR) through a last synthetic step of Pt-catalyzed alkene hydrosilylation then directly employed, without further purification, for the surface modification of quartz and medical grade stainless steel. Subsequent on-surface functionalizations with amine and thiol model molecules demonstrate the potential of these molecular adlayers to be important platforms for future applications in the bioanalytical and biomedical fields.

Single ether group in a glycol-based ultra-thin layer prevents surface fouling from undiluted serum.

Through systematic structural modification, it is shown that the internal, single oxygen atom of simple monoethylene glycol-based organic films is essential for radically altering the fouling behaviour of quartz against undiluted serum, as characterized by the electromagnetic piezoelectric acoustic sensor. The synergy is strongest with distal hydroxyls.

Label-free detection of HIV-2 antibodies in serum with an ultra-high frequency acoustic wave sensor.

Herein is described a label-free immunosensor dedicated to the detection of HIV-2. The biosensor platform is constructed as a mixed self-assembled monolayer-coated quartz wafer onto which HIV-2 immunodominant epitopes are immobilized. The biosensing properties, in terms of specific vs.

Linker immobilization of protein and oligonucleotide on indium-tin-oxide for detection of probe-target interactions by Kelvin physics.

This work describes a label-free microarray analysis technique capable of detecting biomolecule target interactions with probes being anchored with a new linker-diluent system on indium-tin-oxide. The method is based on the differential work function characteristics of the substrate measured by a scanning Kelvin nanoprobe in terms of contact potential difference signals.

A palladium-catalyzed alkylation/direct arylation synthesis of nitrogen-containing heterocycles.

A norbornene-mediated palladium-catalyzed sequence is described in which an alkyl-aryl bond and an aryl-heteroaryl bond are formed in one reaction vessel. The aryl-heteroaryl bond-forming step occurs via a direct arylation reaction. A number of six-, seven-, and eight-membered ring-annulated indoles, pyrroles, pyrazoles, and azaindoles were synthesized from the corresponding bromoalkyl azole and an aryl iodide.

Preparation of annulated nitrogen-containing heterocycles via a one-pot palladium-catalyzed alkylation/direct arylation sequence.

[reaction: see text] A palladium-catalyzed/norbornene-mediated sequential coupling reaction involving an aromatic sp(2) C-H functionalization as the key step is described, in which an alkyl-aryl bond and an aryl-heteroaryl bond are formed in one pot. A variety of highly substituted six- and seven-membered annulated pyrroles and pyrazoles were synthesized in a one-step process in good yields from readily accessible N-bromoalkyl pyrroles or pyrazoles and aryl iodides.

PtCl2-Catalyzed transannular cycloisomerization of 1,5-enynes: a new efficient regio- and stereocontrolled access to tricyclic derivatives.

[reaction: see text] Transannular PtCl(2)-catalyzed cycloisomerizations open a new route to cyclopropanic tricyclic systems. Ketones A or C were efficiently prepared from the same cycloundec-5-en-1-yne precursor B, depending on the substituent at the propargylic position (either benzoate or methoxy).

PtCl2-catalyzed cycloisomerizations of 5-en-1-yn-3-ol systems.

5-En-1-yn-3-ol substrates bearing a free hydroxyl group or an acyl group are highly versatile partners for PtCl2-catalyzed cycloisomerizations. Electrophilic activation of the alkyne moiety triggers at wish a hydride or an O-acyl migration yielding at the end to regioisomeric keto derivatives. The efficient preparation of Sabina ketone, an important monoterpene precursor, has been worked out.

N-silyl-tethered radical cyclizations: a new synthesis of gamma-amino alcohols.

[reaction: see text] Various allylic and propargylic amines bearing a protecting group (PG) have been employed in N-silyl-tethered radical cyclizations. The resulting silapyrrolidine adducts could be smoothly oxidized, creating access to gamma-amino alcohols. The silylation, radical cyclization, and oxidation reactions could be consolidated in a one-pot process.