Acoustic Nebulization Research Articles

Nebulization Swab Assisted Photoionization Tandem Miniaturized Ion Trap Mass Spectrometry for On-Site Analysis of Nonvolatile Compounds.

Nonvolatile compounds usually have a high molecular weight and exhibit a high boiling point, which poses great challenges to the ionization method of MS. Ambient ionization sources can efficiently analyze the nonvolatile compounds without complex pretreatment, but they generally require special media such as heating devices, laser optical devices, or corona needles. Acoustic nebulization assisted photoionization (ANPI) is a potential method for the analysis of nonvolatile compounds that uses nebulization as a prerequisite for photoionization and introduces many advantages of PI, including excellent ionization efficiency, a high yield of molecular ions, and simplified spectrum interpretation. However, the ANPI source can be limited in on-site applications by the complexity of the analytical devices and the high cost of the nebulization chip. To address this issue, in this paper, we explored cheap and commercially piezoelectric materials used in a mist sprayer and fabricated a nebulization swab assisted photoionization (NSAP) as an ambient ionization source. Some useful results are presented: numerical simulation was introduced successfully for optimizing the aerosol distribution in the NSAP source; nonvolatile muscle relaxants, drugs of abuse, antibiotics, phthalates, and cholesterol were detected mostly as their protonated molecular ions while some special acetone/water cluster ions were detected. In addition, the LOD for most of the target analytes ranged from 10.0 to 50.0 pg with RSD ≤ 9%. Finally, this method is implemented for Chinese baijiu spiked with phthalates. The experimental data shows the capability of a NSAP source in high sensitivity and on-site analysis of the nonvolatile compounds.

Inexpensive Ultrasonic Nebulization Coupled with Direct Current Corona Discharge Ionization Mass Spectrometry for Liquid Samples and Its Fundamental Investigations.

The concept of direct mass-spectrometric analysis, especially exploited by ambient desorption/ionization (ADI) methods, provides numerous means for convenient sample analysis. While many simple and versatile ionization sources have been developed, challenges lay in achieving efficient sample introduction. In previous work, a sample introduction method employing direct current corona discharge (CD) coupled to a surface acoustic wave nebulization (SAWN) device enhanced sampling performance for both polar and nonpolar analytes by up to 4 orders of magnitude. In fact, the SAWN-CD method generated a multiply charged peptide ion signal comparable to that of conventional ESI. Unfortunately, the high cost of the SAWN devices themselves limits their accessibility. Herein, we report on an analogous implementation of CD with an inexpensive ultrasonic nebulizer (USN) on the basis of a commercial room humidifier demonstrating equivalent exemplary performance. We subsequently compare the two methods of SAWN-CD and USN-CD in a screening application of milk for the detection of two antibiotic drugs, ciprofloxacin and ampicillin. Finally, we further investigate the relative softness of these CD-coupled acoustic nebulization methods in comparison to that of ESI using a survival yield study of the thermometer ion nitrobenzylpyridinium.

High frequency acoustic nebulization for pulmonary delivery of antibiotic alternatives against Staphylococcus aureus

The increasing prevalence of multidrug resistant bacteria has warranted the search for new antimicrobial agents as existing antibiotics lose their potency. Among these, bacteriophage therapy, as well as the administration of specific bacteriolysis agents, i.e., lytic enzymes, have emerged as attractive alternatives. Nebulizers offer the possibility for delivering these therapeutics directly to the lung, which is particularly advantageous as a non-invasive and direct route to treat bacterial lung infections. Nevertheless, nebulizers can often result in significant degradation of the bacteriophage or protein, both structurally and functionally, due to the large stresses the aerosolization process imposes on these entities. In this work, we assess the capability of a novel low-cost and portable hybrid surface and bulk acoustic wave platform (HYDRA) to nebulize a Myoviridae bacteriophage (phage K) and lytic enzyme (lysostaphin) that specifically targets Staphylococcus aureus. Besides its efficiency in producing phage or protein-laden aerosols within the 1–5 μm respirable range for optimum delivery to the lower respiratory tract where lung infections commonly take place, we observe that the HYDRA platform—owing to the efficiency of driving the aerosolization process at relatively low powers and high frequencies (approximately 10 MHz)—does not result in appreciable denaturation of the phages or proteins, such that the loss of antimicrobial activity following nebulization is minimized. Specifically, a low (0.1 log10 (pfu/ml)) titer loss was obtained with the phages, resulting in a high viable respirable fraction of approximately 90%. Similarly, minimal loss of antimicrobial activity was obtained with lysostaphin upon nebulization wherein its minimum inhibitory concentration (0.5 μg/ml) remained unaltered as compared with the non-nebulized control. These results therefore demonstrate the potential of the HYDRA nebulization platform as a promising strategy for pulmonary administration of alternative antimicrobial agents to antibiotics for the treatment of lung diseases caused by pathogenic bacteria.

Precise drop dispensation on superhydrophobic surfaces using acoustic nebulization

The adhesion forces of liquid drops on superhydrophobic surfaces are typically in the nano-Newton range which presents problems in their dispensation from pipettes. Furthermore, since the liquid adheres more strongly to the pipette tip, some portion of the liquid will tend to remain on the tip, causing inaccuracy in the volume dispensed. We advance a novel approach here, in which the spray from an acoustic nebulizer is sent to a superhydrophobic receptacle and the volume ascertained precisely using a weighing scale. The superhydrophobic surface was identified to develop via a galvanic displacement mechanism in an electroless deposition process. A time dependent morphology change from granular to dendritic with longer immersion into the silver nitrate solution was found which indicated that granular growth beyond a certain size was not feasible, although granular structures were more preferentially formed just after nucleation. The dendritic structure formation was likely due to the natural tendency of the process to maintain or increase the surface area to volume ratio in order not to limit the rate of deposition. An immersion for at least 7 seconds into the silver nitrate solution, when the granular structures were predominant, was all that was needed to ensure superhydrophobicity of the surfaces. Also, the superhydrophobic state required not just significant numbers of the granular structures to be present but also interrupted coverage on the surface. On using the technique, a single drop was created by subsequently covering the receptacle with a lid and shaking it gently. The volume dispensed was found to vary linearly with the operation time of the nebulizer. We elucidated the observed increased ability of drops to reside on inclines using wetting mechanics and presented an elementary mathematical description of the extent of aerosol coverage on the surface, which has implications for the mechanics of aerosol growth into drops. The structural changes in enhanced green fluorescent protein (EGFP) observed after acoustic dispensation necessitated all samples in a fluorimetric assay to involve equal nebulized volumes of the fluorescent protein marker for measurement consistency.