Microwave treatment for improved quality and safety of dehydrated pitted apricots

Dehydrated pitted apricots are widely used as a ready meal ingredient, which renders control of their quality and safety a relevant issue. Pitted apricots are rich in sugars, moisture and organic acids that serve a good medium for microorganisms. Therefore, these products require presale processing. Microwave treatment proved effective for the processing of raw and finished food products. Its impact on microorganisms depends on variant criteria, including taxonomic affiliation, total counts, dielectric cell properties and the treatment dose. The research aimed to study death kinetics in the native dried apricot surface microflora and its growth during subsequent storage. In this respect, we have studied the microwave treatment impact on dried apricot surface microflora depending on treatment dose and determined the residual microflora growth rate during subsequent storage. The doses of 120, 180 and 240 kJ at a 200 W radiation power have been shown to reduce baseline contamination of dehydrated pitted apricots by three orders of magnitude. Statistical kinetics analyses demonstrated a retarded surface microflora growth during subsequent storage. Microwave doses of 120–240 kJ (accounting for ±0.4 lg CFU/g error) exhibited a similar microflora dynamics in subsequent storage. The exposure of dried apricots to a lowest microwave field of 120 kJ ensured stability of the product microbiological dynamics.

Antimicrobial and Antibiofilm Activity of Lys-[Trp6]hy-a1 Combined with Ciprofloxacin Against Gram-Negative Bacteria

Background: Ciprofloxacin (Cip) is the most commonly used quinolone in clinical practice; however large-scale use has favored the increase of multiresistant pathogenic microorganisms. Antimicrobial peptides (AMPs) appear to be a promising alternative in potentiating these conventional drugs. Objective: The aim of this study was to evaluate the effect of the peptide Lys-[Trp6]hy-a1 (lys-a1) on the antimicrobial and antibiofilm activity of ciprofloxacin against clinically relevant gram-negative bacteria. Methods: The antimicrobial effects of Cip and lys-a1 were assessed by determining the minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs). The synergistic action of Cip and lys-a1 was determined by checkerboard assay. The time-kill curve was constructed for the Cip/lys-a1 combination against Pseudomonas aeruginosa ATCC 9027. The antibiofilm activity of this combination was analyzed by crystal violet, colony-forming unit count and atomic force microscopy (AFM). Results: The data demonstrated that lys-a1 was able to inhibit planktonic growth of strains of P. aeruginosa and Klebsiella pneumoniae both at 125 μg/mL. The fractional inhibitory concentration index (FICi) showed a synergistic effect between Cip and lys-a1 against P. aeruginosa, decreasing the MICs of the individual antimicrobial agents by 4- and 8-fold, respectively. This effect was also observed for the death kinetics and antibiofilm activity. Analysis of the early biofilms (6 h) as well as isolated cells by AFM images evidenced the cell perturbation caused by Cip/lys-a1 treatment. Conclusion: These data suggest that lys-a1 has biotechnological potential as a therapeutic tool for the treatment of infections caused by clinically relevant microorganisms, especially P. aeruginosa.

Nanoscale Organization of FasL on DNA Origami as a Versatile Platform to Tune Apoptosis Signaling in Cells

Nanoscale probes with fine-tunable properties are of key interest in cell biology and nanomedicine to elucidate and eventually control signaling processes in cells. A critical, still challenging issue is to conjugate these probes with molecules in a number- and spatially-controlled manner. Here, DNA origami-based nanoagents as nanometer precise scaffolds presenting Fas ligand (FasL) in well-defined arrangements to cells are reported. These nanoagents activate receptor molecules in the plasma membrane initiating apoptosis signaling in cells. Signaling for apoptosis depends sensitively on FasL geometry: fastest time-to-death kinetics are obtained for FasL nanoagents representing predicted structure models of hexagonal receptor ordering with 10 nm inter-molecular spacing. Slower kinetics are observed for one to two FasL on DNA origami or FasL coupled with higher flexibility. Nanoagents with FasL arranged in hexagons with small (5 nm) and large (30 nm) spacing impede signal transduction. Moreover, for predicted hexagonal FasL nanoagents, signaling efficiency is faster and 100× higher compared to naturally occurring soluble FasL. Incubation of the FasL-origami nanoagent in solution exhibited an EC50 value of only 90 pM. These studies present DNA origami as versatile signaling platforms to probe the significance of molecular number and nanoscale ordering for signal initiation in cells.