Cellulose nanocrystal-mediated synthesis of silver nanoparticles: role of sulfate groups in nucleation phenomena.

Developing sustainable chemical methods to synthesize silver nanoparticles has drawn significant research interest. Due to their unique and well-defined physical-chemical properties, cellulose nanocrystals (CNCs) have become one of the most promising renewable nanomaterials. Here we use CNC to mediate silver nanoparticle synthesis and elucidate the effect of CNC surface chemistry (as defined by sulfate groups) in nanoparticle formation and nucleation in the presence of borohydride reduction. Pristine CNCs produced by sulfuric acid hydrolysis and partially desulfated CNCs mediated the formation of silver nanoparticles of different sizes (and size distribution) following different rates of formation, as determined by transmission electron microscopy (TEM) and UV-vis spectroscopy. The results shed light on methods to stabilize silver nanoparticles, control their nucleation, and highlight the potential of CNCs in metal nanoparticle synthesis.

Disposable Microfluidic Sensor Based on Nanocellulose for Glucose Detection.

Point-of-care devices that are inexpensive, disposable, and environmentally friendly are becoming increasingly predominant in the field of biosensing and biodiagnostics. Here, microfluidics is a suitable option to endow portability and minimal reagent and material consumption. Nanocellulose is introduced to manufacture microfluidic channels and as a storage and immobilization compartment of glucose oxidase. Improved enzymatic activity retention is demonstrated in a simple and disposable point-of-care diagnostic unit that is able to detect glucose from fluid matrices at 0.1 × 10-3 m concentration and in less than 10 min. It is concluded that the patterning and fluidic technologies that are possible with nanocellulose enable easily scalable multianalyte designs.

Fluorescent boronic acid polymer grafted on silica particles for affinity separation of saccharides.

Boronic acid affinity gels are important for effective separation of biological active cis-diols, and are finding applications both in biotech industry and in biomedical research areas. To increase the efficacy of boronate affinity separation, it is interesting to introduce repeating boronic acid units in flexible polymer chains attached on solid materials. In this work, we synthesize polymer brushes containing boronic acid repeating units on silica gels using surface-initiated atom transfer radical polymerization (ATRP). A fluorescent boronic acid monomer is first prepared from an azide-tagged fluorogenic boronic acid and an alkyne-containing acrylate by Cu(I)-catalyzed 1,3-dipolar cycloaddition reaction (the CuAAC click chemistry). The boronic acid monomer is then grafted to the surface of silica gel modified with an ATRP initiator. The obtained composite material contains boronic acid polymer brushes on surface and shows favorable saccharide binding capability under physiological pH conditions, and displays interesting fluorescence intensity change upon binding fructose and glucose. In addition to saccharide binding, the flexible polymer brushes on silica also enable fast separation of a model glycoprotein based on selective boronate affinity interaction. The synthetic approach and the composite functional material developed in this work should open new opportunities for high efficiency detection, separation, and analysis of not only simple saccharides, but also glycopeptides and large glycoproteins.

Photoconjugation of molecularly imprinted polymer with magnetic nanoparticles.

Because of their synthetic accessibility, molecularly imprinted polymer (MIP) nanoparticles are ideal building blocks for preparing multifunctional composites. In this work, we developed a general photocoupling chemistry to enable simple conjugation of MIP nanoparticles with inorganic magnetic nanoparticles. We first synthesized MIP nanoparticles using propranolol as a model template and perfluorophenyl azide-modified silica-coated magnetic nanoparticles. Using a simple photoactivation followed by facile purification with a magnet, we obtained magnetic composite particles that showed selective uptake of propranolol. We characterized the nanoparticles and composite materials using FT-IR, TEM, fluorescence spectroscopy, and radioligand binding analysis. Through the high molecular selectivity of the magnetic composite, we demonstrated the nondestructive feature and the high efficiency of the photocoupling chemistry. The versatile photoconjugation method developed in this work should also be very useful for combining organic MIPs with other inorganic nanoparticles to enable new chemical sensors and high efficiency photocatalysts.