Ultra-rapid elimination of biofilms via the combustion of a nanoenergetic coating.

BACKGROUND: Biofilms occur on a wide variety of surfaces including metals, ceramics, glass etc. and often leads to accumulation of large number of various microorganisms on the surfaces. This biofilm growth is highly undesirable in most cases as biofilms can cause degradation of the instruments and its performance along with contamination of the samples being processed in those systems. The current "offline" biofilm removal methods are effective but labor intensive and generates waste streams that are toxic to be directly disposed. We present here a novel process that uses nano-energetic materials to eliminate biofilms in < 1 second. The process involves spray-coating a thin layer of nano-energetic material on top of the biofilm, allowing it to dry, and igniting the dried coating to incinerate the biofilm. RESULTS: The nanoenergetic material is a mixture of aluminum (Al) nanoparticles dispersed in a THV-220A (fluoropolymer oxidizer) matrix. Upon ignition, the Al nanoparticles react with THV-220A exothermically, producing high temperatures (>2500 K) for an extremely brief period (~100 ms) that destroys the biofilm underneath. However, since the total amount of heat produced is low (~0.1 kJ/cm2), the underlying surface remains undamaged. Surfaces with biofilms of Pseudomonas aeruginosa initially harboring ~ 10(7) CFU of bacteria /cm2 displayed final counts of less than 5 CFU/cm2 after being subjected to our process. The byproducts of the process consist only of washable carbonaceous residue and gases, making this process potentially inexpensive due to low toxic-waste disposal costs. CONCLUSIONS: This novel method of biofilm removal is currently in the early stage of development. However, it has potential to be used in offline biofilm elimination as a rapid, easy and environmentally friendly method.

Kinetically limited differential centrifugation as an inexpensive and readily available alternative to centrifugal elutriation.

When separating two species with similar densities but differing sedimentation velocities (because of differences in size), centrifugal elutriation is generally the method of choice. However, a major drawback to this approach is the requirement for specialized equipment. Here, we present a new method that achieves similar separations using standard benchtop centrifuges by loading the seperands as a layer on top of a dense buffer of a specified length, and running the benchtop centrifugation process for a calculated amount of time, thereby ensuring that all faster moving species are collected at the bottom, while all slower moving species remain in the buffer. We demonstrate the use of our procedure to isolate bacteria from blood culture broth (a mixture of bacterial growth media, blood, and bacteria).

Sputter-deposition of silver nanoparticles into ionic liquid as a sacrificial reservoir in antimicrobial organosilicate nanocomposite coatings.

We present a new approach for fabricating robust, regenerable antimicrobial coatings containing an ionic liquid (IL) phase incorporating silver nanoparticles (AgNPs) as a reservoir for Ag(0)/Ag(+) species within sol-gel-derived nanocomposite films integrating organosilicate nanoparticles. The IL serves as an ultralow volatility (vacuum-compatible) liquid target, allowing for the direct deposition and dispersion of a high-density AgNP "ionosol" following conventional sputtering techniques. Two like-anion ILs were investigated in this work: methyltrioctylammonium bis(trifluoromethylsulfonyl)imide, [N(8881)][Tf(2)N], and 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, [emim][Tf(2)N]. Silver ionosols derived from these two ILs were incorporated into silica-based sol-gel films and the resultant antimicrobial activity evaluated against Pseudomonas aeruginosa bacteria. Imaging of the surface morphologies of the as-prepared films established a link between an open macroporous film architecture and the observation of high activity. Nanocomposites based on [N(8881)][Tf(2)N] displayed excellent antimicrobial activity against P. aeruginosa over multiple cycles, reducing cell viability by 6 log units within 4 h of contact. Surprisingly, similar films prepared from [emim][Tf(2)N] presented negligible antimicrobial activity, an observation we attribute to the differing abilities of these IL cations to infiltrate the cell wall, regulating the influx of silver ions to the bacterium's interior.

Development and in vitro studies of a polyethylene terephthalate-gold nanoparticle scaffold for improved biocompatibility.

Polyethylene terephthalate (PET) mesh is one of the most commonly used synthetic biomaterials for tension-free hernia repair. In an effort to improve the biocompatibility of PET mesh, gold nanoparticles (AuNP) in various concentrations were conjugated to the PET surface to develop PET-AuNP scaffolds. These novel scaffolds were characterized with Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and differential scanning calorimetry (DSC) to assess the addition of functional groups, presence of AuNPs, and thermal stability of the modified PET mesh, respectively. The biocompatibility of the PET-AuNP scaffolds was evaluated through in vitro cell culture assays. The cellularity of cells exposed to the PET-AuNP scaffolds, as well as the scaffolds' ability to reduce reactive oxygen species, was assessed using L929 murine fibroblasts. Antimicrobial properties of AuNPs conjugated to PET mesh were tested against the bacteria Pseudomonas aeruginosa. Results from the FT-IR showed presence of COOH groups while SEM displayed bonding of AuNPs to the PET surface. DSC results indicated that the PET more than likely did not undergo any detrimental degradation due to the surface modification. Results from the in vitro studies showed that AuNPs, in optimal concentrations (1× concentrations), enhanced cellularity, reduced ROS, and reduced bacteria adhesion to PET. These studies demonstrated enhanced biocompatibility of the AuNP conjugated PET mesh over pristine PET mesh.

Novel electrical method for early detection of viable bacteria in blood cultures.

We present a novel electrical method for detecting viable bacteria in blood cultures that is 4 to 10 times faster than continuous monitoring blood culture systems (CMBCS) like the Bactec system. Proliferating bacteria are detected via an increase in the bulk capacitance of suspensions, and the threshold concentration for detection is ∼ 10(4) CFU/ml (compared to ∼ 10(8) CFU/ml for the Bactec system).

Characterization of cold-active uracil-DNA glycosylase from Bacillus sp. HJ171 and its use for contamination control in PCR.

In this study, the gene encoding Bacillus sp. HJ171 uracil-DNA glycosylase (Bsp HJ171 UDG) was cloned and sequenced. The Bsp HJ171 UDG gene consists of a 738-bp DNA sequence, which encodes for a protein that is 245-amino-acid residues in length. The deduced amino acid sequence of the Bsp HJ171 UDG had a high sequence similarity with other bacterial UDGs. The molecular mass of the protein derived from this amino acid sequence was 27.218 kDa. The Bsp HJ171 UDG gene was expressed under the control of a T7lac promoter in the pTYB1 plasmid in Escherichia coli BL21 (DE3). The expressed enzyme was purified in one step using the Intein Mediated Purification with an Affinity Chitin-binding Tag purification system. The optimal temperature range, pH, NaCl concentration, and KCl concentration of the purified enzyme was 20-25 degrees C, 8.0, 25 and 25 mM, respectively. The half-life of the enzyme at 40 degrees C and 50 degrees C were approximately 131 and 45 s, respectively. These heat-labile characteristics enabled Bsp HJ171 UDG to control carry-over contamination in the polymerase chain reaction product (PCR) without losing the PCR product.

Kenojeinin I, antimicrobial peptide isolated from the skin of the fermented skate, Raja kenojei.

An antimicrobial peptide was purified from fermented skate skin extract using the solid-phase extraction and separation on HPLC reversed-phase chromatography. Amino acid sequence of the purified peptide (Peak A) having an antimicrobial activity revealed the presence of many cationic residues of the total 28 amino acids. Its molecular mass was found to be 3059 Da. This result was in excellent agreement with the theoretical molecular mass calculated from the amino acid sequence. The synthetic kenojeinin I had inhibitory effects on B. subtilis (MIC, 12 microg/ml), E. coli (28 microg/ml), and S. cerevisiae (12 microg/ml). These results indicate that fermented skate skin is potentially antimicrobial.