SARS-CoV-2 Inactivation on Hard Non-porous Airplane Cabin Material Surfaces was Limited After Exposure to Far UV-C (222 nm) Radiation.

AIMS: To test the efficacy of 222 nm Far UV-C for surface disinfection of SARS-CoV-2 on inanimate surfaces from airplane cabins. METHODS AND RESULTS: Two far ultraviolet (UV-C) irradiation light systems were evaluated for disinfection of SARS-CoV-2. Materials used for carriers (test surfaces) included polished stainless steel and used airplane materials including seatbelt latches, window dust covers, sidewall laminates, and tray tables. CONCLUSIONS: While demonstrating reasonable efficacy under some experimental conditions, the data indicated that 222 nm Far UV-C disinfection alone does not reliably provide a 3 log10 or 99.9% reduction of SARS-CoV-2 on inanimate surfaces from an airplane cabin. An Ushio (Cypress, CA) 1.7" x 2.3" Care222® 12W 222nm BI lamp module tested in triplicate at a low (⁓ 1.5 mJ cm-2), medium (⁓ 3.0 mJ cm-2), and high (⁓ 6 to 9 mJ cm-2) fluence did not provide a ≥ 3 log10 or 99.9% reduction of SARS-CoV-2. The reduction of SARS-CoV-2 was greatest on stainless steel. The result was a log10 reduction of 2.83, 1.33, 2.58, and 2.21 logs for virus samples containing saline, saline with 2.5 mg BSA, saline with 0.25 mg BSA, and artificial saliva respectively at a dosage of 5 to 9 mJ cm-2. The log10 reduction of SARS-CoV-2 in saline with 2.5 mg bovine serum albumin was lowest with 1.33 for stainless steel, 0.93 for belt latch, and 0.61 for tray table at a dosage of 5 to 6 mJ cm-2.The second UV lighting system tested was a prototype mobile wand with a built-in short-pass filtered krypton-chloride cylindrical lamp. One pass of the wand over a tray holding carriers inoculated with SARS-CoV-2 in artificial saliva at a rate of approximately 1 foot (1') per second (sec) exposed the carriers to 7.3 mJ cm-2. The log10 reductions determined for the single pass were 2.97, 3.75, 1.78, 1.91, and 1.28 logs for stainless steel, belt latch, dust cover, sidewall, and tray table respectively. Two passes of the wand generated 17.2 mJ cm-2 and resulted in log10 reductions of 4.04, 3.74, 4.24, 3.68, and 1.66 logs for stainless steel, belt latch, dust cover, sidewall, and tray table respectively. The combination of higher fluence from multiple passes of the wand, the close proximity (10 cm wand to the carrier), the exposure to elevated temperatures up to 35°C, and ozone from the bulb being blown directly onto the carriers contributed to effective viral inactivation on all surfaces except the airplane tray table. The impact of temperature and ozone on viral inactivation should be determined for future testing of the 222 nm UV-C wand.

Multidimensional analysis of denatured milk proteins by hydrophobic interaction chromatography coupled to a dynamic surface tension detector.

Multidimensional analysis of denatured milk proteins is reported using high-performance liquid chromatography (HPLC) combined with dynamic surface tension detection (DSTD). A hydrophobic interaction chromatography (HIC) column (a TSK-Gel Phenyl-5PW column, TosoBiosep), in the presence of 3.0 M guanidine hydrochloride (GdmHCl) as denaturing agent is employed as the mobile phase. Dynamic surface tension is measured through the differential pressure across the liquid-air interface of repeatedly growing and detaching drops. Continuous surface tension measurement throughout the entire drop growth (50 ms to 4 s) is achieved, for each eluting drop of 4 s length, providing insight into both the kinetic and thermodynamic behavior of molecular orientation processes at the liquid-air interface. An automated calibration procedure and data analysis method is applied with the DSTD system, which allows two unique solvents to be used, the HIC mobile phase for the sample and a second solvent (water for example) for the standard, permitting real-time dynamic surface tension data to be obtained. Three-dimensional data is obtained, with surface tension as a function of drop time first converted to surface pressure, which is plotted as a function of the chromatographic elution time axis. Experiments were initially performed using flow injection analysis (FIA) with the DSTD system for investigating commercial single standard milk proteins (alpha-lactalbumin, beta-lactoglobulin, alpha-, beta-, kappa-casein and a casein mixture) denatured by GdmHCl. These FIA-DSTD experiments allowed the separation and detection conditions to be optimized for the HIC-DSTD experiments. Thus, the HIC-DSTD system has been optimized and successfully applied to the selective analysis of surface-active casein fractions (alpha s1- and beta-casein) in a commercial casein mixture, raw milk samples (cow's, ewe's and goat's milk) and other diary products (yogurt, stracchino, mozzarella, parmesan cheese and chocolate cream). The different samples were readily distinguished based upon the selectivity provided by the HIC-DSTD method. The selectivity advantage of using DSTD relative to absorbance detection is also demonstrated.

Post-column fluorescence derivatization of proteins and peptides in capillary electrophoresis with a sheath flow reactor and 488 nm argon ion laser excitation.

We report the use of a sheath flow reactor for post-column fluorescence derivatization of proteins. The derivatization reaction employed naphthalene-2,3-dicarboxaldehyde (NDA) and beta-mercaptoethanol, which were added in the sheath buffer. The labeled proteins were detected by laser-induced fluorescence with an argon-ion laser beam at 488 nm. The performance of this detection scheme was evaluated by separation of some protein standards. A column efficiency of 450,000 plates/m was obtained without stacking. The limits of detection for those standard proteins were determined to be from 8 to 32 nM. Excellent linear relationship was obtained with correlation coefficient of 0.9998 for alpha-lactalbumin concentration ranging from 3.91 x 10(-7) to 1.25 x 10(-5) M. Separation of protein standards at low pH was also demonstrated by reversing the electroosmotic flow (EOF) with addition of cetyltrimethylammonium bromide (CTAB) to the running buffer. Different separation selectivity was achieved, but the sensitivity is poorer than that at high pH. This post-column derivatization detection system was applied successfully to analyze the protein extract from HT29 human colon cancer cells as well as tryptic peptides.

Determination, by dynamic surface-tension analysis, of the molar mass of proteins denatured in guanidine thiocyanate.

A drop-based dynamic surface-tension detector (DSTD) has been used to study the dynamic surface tension behavior of proteins denatured in guanidine thiocyanate (GndSCN). The dynamic surface tension at the air-liquid interface is obtained by measuring the internal pressure of drops that grow and detach at a specified rate. In the method the sample of interest is injected and subsequently flows to the DSTD-sensing capillary tip. For this work, a novel DSTD calibration procedure utilizing two distinct mobile phases is applied. Here, the mobile phases are aqueous with different constituents, for example GndSCN and phosphate buffer, either added or omitted. The dual-mobile phase calibration procedure gives the analyst the capability of making protein measurements in a GndSCN-phosphate buffer mobile phase, while measuring a calibration standard in another mobile phase, such as water, in which the surface tension of the calibration standard is readily available. Results are presented with drop volumes of either 2 microL (i.e. 2-s drops) or 7 microL (i.e. 7-s drops) for proteins varying in molar mass from 12,000 to 330,000 g mol(-1). We demonstrate that the DSTD can be used to determine the molar mass of proteins denatured in GndSCN. The method applies a regime where the denatured protein is detected by surface-active properties, and selectivity with regard to molar mass is contained in the dynamic component of the DSTD signal. The dynamic surface pressure signals of the denatured proteins suggest that diffusion plays a large role in the kinetics of the surface activity. The limit of detection for the denatured proteins studied ranged from 3 mg L(-1) to 14 mg L(-1). The DSTD, coupled with the novel dual-mobile phase calibration procedure, can be used to investigate the fundamental properties of proteins. Insight into the behavior at the air-liquid interface for native and denatured proteins is achieved; this is a novel tool for studying protein denaturation, complementary to other common approaches such as spectroscopy and calorimetry. Furthermore, the reported method could be widely applied to the study of effects on the interfacial properties of proteins after a variety of chemical and physical modifications that are possible with the dual-mobile phase calibration procedure.

Sequential injection analysis with dynamic surface tension detection High throughput analysis of the interfacial properties of surface-active samples.

A sequential injection analysis (SIA) system is coupled with dynamic surface tension detection (DSTD) for the purpose of studying the interfacial properties of surface-active samples. DSTD is a novel analyzer based upon a growing drop method, utilizing a pressure sensor measurement of drop pressure. The pressure signal depends on the surface tension properties of sample solution drops that grow and detach at the end of a capillary tip. In this work, SIA was used for creating a reagent concentration gradient, and for blending the reagent gradient with a steady-state sample. The sample, consisting of either sodium dodecyl sulfate (SDS) or poly(ethylene glycol) at 1470 g mol(-1) (PEG 1470), elutes with a steady-state concentration at the center of the sample plug. Reagents such as Brij(R)35, tetrabutylammonium (TBA) hydroxide and beta-cyclodextrin were introduced as a concentration gradient that begins after the sample plug has reached the steady-state concentration. By blending the reagent concentration gradient with the sample plug using SIA/DSTD, the kinetic surface pressure signal of samples mixed with various reagent concentrations is observed and evaluated in a high throughput fashion. It was found that the SIA/DSTD method consumes lesser reagent and required significantly less analysis time than traditional FIA/DSTD. Four unique chemical systems were studied with regard to how surface activity is influenced, as observed through the surface tension signal: surface activity addition, surface activity reduction due to competition, surface activity enhancement due to ion-pair formation, and surface activity reduction due to bulk phase binding chemistry.