Improvement of catalytic efficiency of immobilized enzymes via materials engineering was demonstrated through the preparation of bioactive nanofibers. Bioactive polystyrene (PS) nanofibers with a typical diameter of 120 nm were prepared and examined for catalytic efficiency for biotransformations. The nanofibers were produced by electrospinning functionalized PS, followed by the chemical attachment of a model enzyme, alpha-chymotrypsin. The observed enzyme loading as determined by active site titration was up to 1.4% (wt/wt), corresponding to over 27.4% monolayer coverage of the external surface of nanofibers. The apparent hydrolytic activity of the nanofibrous enzyme in aqueous solutions was over 65% of that of the native enzyme, indicating a high catalytic efficiency as compared to other forms of immobilized enzymes. Furthermore, nanofibrous alpha-chymotrypsin exhibited a much-improved nonaqueous activity that was over 3 orders of magnitude higher than that of its native counterpart suspended in organic solvents including hexane and isooctane. It appeared that the covalent binding also improved the enzyme's stability against structural denaturation, such that the half-life of the nanofibrous enzyme in methanol was 18-fold longer than that of the native enzyme.

Nanoparticles provide an ideal remedy to the usually contradictory issues encountered in the optimization of immobilized enzymes: minimum diffusional limitation, maximum surface area per unit mass, and high effective enzyme loading. In addition to the promising performance features, the unique solution behaviors of the nanoparticles also point to a transitional region between the heterogeneous (with immobilized enzymes) and homogeneous (with soluble free enzymes) catalysis. The particle mobility, which is related to particle size and solution viscosity through Stokes-Einstein equation, may impact the reaction kinetics according to the collision theory. The mobility-activity relationship was examined through experimental studies and theoretical modeling in the present work. Polystyrene particles with diameters ranging from 110-1000 nm were prepared. A model enzyme, alpha-chymotrypsin, was covalently attached to the nanoparticles up to 6.6 wt%. The collision theory model was found feasible in correlating the catalytic activities of particles to particle size and solution viscosity. Changes in the size of particles and the viscosity of reaction media, which all affect the mobility of the enzyme catalyst, evidently altered the intrinsic activity of the particle-attached enzyme. Compared to K(M), k(cat) appeared to be less sensitive to particle size and viscosity.

Perhydrolase S54V (AcT) effectively catalyzes the perhydrolysis of propylene glycol diacetate (PGD) to generate peracetic acid (PAA). PAA is a potent oxidant used for sanitization and disinfection, with broad effectiveness against bacteria, yeasts, fungi, and spores. In this study, active and stable composites are developed by incorporating AcT–carbon nanotube conjugates into polymer and latex‐based paint. At a conjugate loading of 0.16% (w/v), the composite generated 11 mM PAA in 20 min, capable of killing more than 99% spores initially charged at 106 colony‐forming units per milliliter.

Infection with antibiotic-resistant pathogens such as methicillin-resistant Staphylococcus aureus (MRSA) is one of the primary causes of hospitalizations and deaths. To address this issue, we have designed antimicrobial coatings incorporating carbon nanotube-enzyme conjugates that are highly effective against antibiotic-resistant pathogens. Specifically, we incorporated conjugates of carbon nanotubes with lysostaphin, a cell wall degrading enzyme, into films to impart bactericidal properties against Staphylococcus aureus and Staphylococcus epidermidis. We fabricated and characterized nanocomposites containing different conjugate formulations and enzyme loadings. These enzyme-based composites were highly efficient in killing MRSA (>99% within 2 h) without release of the enzyme into solution. Additionally, these films were reusable and stable under dry storage conditions for a month. Such enzyme-based film formulations may be used to prevent growth of pathogenic and antibiotic-resistant microorganisms on various common surfaces in hospital settings. Polymer and paint films containing such antimicrobial conjugates, in particular, could be advantageous to prevent risk of staphylococcal-specific infection and biofouling.Keywords carbon nanotube; lysostaphin; nanocomposite; antimicrobial film; methicillin-resistant Staphylococcus aureus (MRSA) It is estimated that out of the expected 2 billion people carrying Staphylococcus aureus (S. aureus) worldwide, up to 53 million individuals are infected with methicillin-resistant S. aureus (MRSA).1 Specifically, S. aureus -related diseases such as septicemia and pneumonia are responsible for a large number of hospitalizations (ca. 480,000 in 2005) and deaths (nearly 11,000 in 2005) in the U.S., alone.2 Staphylococcal infection caused by S. aureus and Staphylococcus epidermidis (S. epidermidis) is also a major concern in patients with indwelling devices such as catheters, heart valves, and prostheses.3 While medical and surgical equipment, hospital rooms, and various other objects in hospital settings provide an kaner@rpi.edu, dordick@rpi.edu. Supporting Information Available: Mechanism of Lst-mediated cell wall degradation, bactericidal activity of films against S. epidermidis, bactericidal efficiency of six-times washed films, and SEM characterization of films with different Lst loadings. This material is available free of charge via the Internet at http://pubs.acs.org. NIH Public AccessAuthor Manuscript ACS Nano. Author manuscript; available in PMC 2011 July 27.Published in final edited form as: ACS Nano. 2010 July 27; 4(7): 3993-4000. doi:10.1021/nn100932t. NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author Manuscript easily accessible platform for pathogenic bacteria to settle and proliferate, any surface once touched by an infected person serves as a breeding ground for such pathogens.Considering the magnitude of pathogen-related complications and the assistance of various surfaces in growth and spread of these pathogens, significant attention has ...

The long and short of it: A regioselective enzyme‐catalyzed acylation of the disaccharide trehalose generated a family of low‐molecular‐weight gelators with unprecedented properties. The selectivity of enzymatic catalysis enables direct control over gelation properties by simply varying the acyl‐chain length to give gelation in solvents ranging from the highly hydrophilic acetonitrile to the highly hydrophobic cyclohexane.