Polymer Brushes on Silica Nanostructures Prepared by Aminopropylsilatrane Click Chemistry: Superior Antifouling and Biofunctionality.

In nanobiotechnology, the importance of controlling interactions between biological molecules and surfaces is paramount. In recent years, many devices based on nanostructured silicon materials have been presented, such as nanopores and nanochannels. However, there is still a clear lack of simple, reliable, and efficient protocols for preventing and controlling biomolecule adsorption in such structures. In this work, we show a simple method for passivation or selective biofunctionalization of silica, without the need for polymerization reactions or vapor-phase deposition. The surface is simply exposed stepwise to three different chemicals over the course of ∼1 h. First, the use of aminopropylsilatrane is used to create a monolayer of amines, yielding more uniform layers than conventional silanization protocols. Second, a cross-linker layer and click chemistry are used to make the surface reactive toward thiols. In the third step, thick and dense poly(ethylene glycol) brushes are prepared by a grafting-to approach. The modified surfaces are shown to be superior to existing options for silica modification, exhibiting ultralow fouling (a few ng/cm2) after exposure to crude serum. In addition, by including a fraction of biotinylated polymer end groups, the surface can be functionalized further. We show that avidin can be detected label-free from a serum solution with a selectivity (compared to nonspecific binding) of more than 98% without the need for a reference channel. Furthermore, we show that our method can passivate the interior of 150 nm × 100 nm nanochannels in silica, showing complete elimination of adsorption of a sticky fluorescent protein. Additionally, our method is shown to be compatible with modifications of solid-state nanopores in 20 nm thin silicon nitride membranes and reduces the noise in the ion current. We consider these findings highly important for the broad field of nanobiotechnology, and we believe that our method will be very useful for a great variety of surface-based sensors and analytical devices.

The Potential Role of Functional Near-Infrared Spectroscopy as Clinical Biomarkers in Schizophrenia.

Functional near-infrared spectroscopy (fNIRS) is a recently developed technique that can measure hemoglobin changes in the cerebral cortex, and fNIRS-based research in psychiatry has been progressing rapidly. fNIRS is advantageous in its noninvasiveness, ease of administration, tolerance of small movements, inexpensiveness, strong signal correlations with fMRI signals, and in providing imaging with excellent time resolution and moderate spatial resolution. However, fNIRS has several disadvantages, such as low spatial resolution and shallower measurements in brain regions compared with other functional neuroimaging techniques (e.g. functional magnetic resonance imaging and positron emission tomography). Therefore, fNIRS may be a candidate instrument for clinical use in psychiatry, as it can measure brain activity in a clinical setting. Moreover, previous studies have demonstrated that altered brain activity in the prefrontal cortex is associated with clinical symptoms and functional outcomes in patients with schizophrenia, suggesting that fNIRS could be used as a potential biomarker. Future studies aimed at exploring fNIRS differences in different clinical stages, longitudinal changes, medication effects, variations during different cognitive task paradigms, cross-cultural comparisons, and applying more delicate statistical analytic methodologies are warranted to develop more accurate biomarkers that can be applied in clinical practice for differential diagnosis, monitoring symptoms, predicting functional outcomes, and the personalized decision regarding treatment options in patients with schizophrenia.