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Communications Biology Aug 2021Lipid Nanoparticles (LNPs) are used to deliver siRNA and COVID-19 mRNA vaccines. The main factor known to determine their delivery efficiency is the pKa of the LNP...
Lipid Nanoparticles (LNPs) are used to deliver siRNA and COVID-19 mRNA vaccines. The main factor known to determine their delivery efficiency is the pKa of the LNP containing an ionizable lipid. Herein, we report a method that can predict the LNP pKa from the structure of the ionizable lipid. We used theoretical, NMR, fluorescent-dye binding, and electrophoretic mobility methods to comprehensively measure protonation of both the ionizable lipid and the formulated LNP. The pKa of the ionizable lipid was 2-3 units higher than the pKa of the LNP primarily due to proton solvation energy differences between the LNP and aqueous medium. We exploited these results to explain a wide range of delivery efficiencies in vitro and in vivo for intramuscular (IM) and intravascular (IV) administration of different ionizable lipids at escalating ionizable lipid-to-mRNA ratios in the LNP. In addition, we determined that more negatively charged LNPs exhibit higher off-target systemic expression of mRNA in the liver following IM administration. This undesirable systemic off-target expression of mRNA-LNP vaccines could be minimized through appropriate design of the ionizable lipid and LNP.
Topics: Administration, Intravenous; Animals; Drug Compounding; Gene Expression; Humans; Hydrogen-Ion Concentration; Injections, Intramuscular; Ions; Lipids; Mice; Molecular Structure; Nanoparticles; RNA, Messenger; Spectrum Analysis; Tissue Distribution; Transfection
PubMed: 34381159
DOI: 10.1038/s42003-021-02441-2 -
Mass Spectrometry Reviews Sep 2022Mass spectrometry imaging (MSI) combines molecular and spatial information in a valuable tool for a wide range of applications. Matrix-assisted laser... (Review)
Review
Mass spectrometry imaging (MSI) combines molecular and spatial information in a valuable tool for a wide range of applications. Matrix-assisted laser desorption/ionization (MALDI) is at the forefront of MSI ionization due to its wide availability and increasing improvement in spatial resolution and analysis speed. However, ionization suppression, low concentrations, and endogenous and methodological interferences cause visualization problems for certain molecules. Chemical derivatization (CD) has proven a viable solution to these issues when applied in mass spectrometry platforms. Chemical tagging of target analytes with larger, precharged moieties aids ionization efficiency and removes analytes from areas of potential isobaric interferences. Here, we address the application of CD on tissue samples for MSI analysis, termed on-tissue chemical derivatization (OTCD). MALDI MSI will remain the focus platform due to its popularity, however, alternative ionization techniques such as liquid extraction surface analysis and desorption electrospray ionization will also be recognized. OTCD reagent selection, application, and optimization methods will be discussed in detail. MSI with OTCD is a powerful tool to study the spatial distribution of poorly ionizable molecules within tissues. Most importantly, the use of OTCD-MSI facilitates the analysis of previously inaccessible biologically relevant molecules through the adaptation of existing CD methods. Though further experimental optimization steps are necessary, the benefits of this technique are extensive.
Topics: Image Processing, Computer-Assisted; Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
PubMed: 33433028
DOI: 10.1002/mas.21680 -
Molecules (Basel, Switzerland) Jun 2021Non-targeted screening (NTS) with reversed phase liquid chromatography electrospray ionization high resolution mass spectrometry (LC/ESI/HRMS) is increasingly employed... (Review)
Review
Non-targeted screening (NTS) with reversed phase liquid chromatography electrospray ionization high resolution mass spectrometry (LC/ESI/HRMS) is increasingly employed as an alternative to targeted analysis; however, it is not possible to quantify all compounds found in a sample with analytical standards. As an alternative, semi-quantification strategies are, or at least should be, used to estimate the concentrations of the unknown compounds before final decision making. All steps in the analytical chain, from sample preparation to ionization conditions and data processing can influence the signals obtained, and thus the estimated concentrations. Therefore, each step needs to be considered carefully. Generally, less is more when it comes to choosing sample preparation as well as chromatographic and ionization conditions in NTS. By combining the positive and negative ionization mode, the performance of NTS can be improved, since different compounds ionize better in one or the other mode. Furthermore, NTS gives opportunities for retrospective analysis. In this tutorial, strategies for semi-quantification are described, sources potentially decreasing the signals are identified and possibilities to improve NTS are discussed. Additionally, examples of retrospective analysis are presented. Finally, we present a checklist for carrying out semi-quantitative NTS.
PubMed: 34207787
DOI: 10.3390/molecules26123524 -
Molecular & Cellular Proteomics : MCP Jul 2011Electrospray ionization is today the most widely used ionization technique in chemical and biochemical analysis. Interfaced with a mass spectrometer it allows the... (Review)
Review
Electrospray ionization is today the most widely used ionization technique in chemical and biochemical analysis. Interfaced with a mass spectrometer it allows the investigation of the molecular composition of liquid samples. With electrospray a large variety of chemical substances can be ionized. There is no limitation in mass which thus enables even the investigation of large noncovalent protein complexes. Its high ionization efficiency profoundly changed biomolecular sciences because proteins can be identified and quantified on trace amounts in a high throughput fashion. This review article focuses mainly on the exploration of the underlying ionization mechanism. Some ionization characteristics are discussed that are related to this mechanism. Typical spectra of peptides, proteins, and noncovalent complexes are shown and the quantitative character of spectra is highlighted. Finally the possibilities and limitations in measuring the association constant of bivalent noncovalent complexes are described.
Topics: Models, Chemical; Peptide Fragments; Protein Binding; Proteins; Spectrometry, Mass, Electrospray Ionization
PubMed: 21742801
DOI: 10.1074/mcp.M111.009407 -
Frontiers in Chemistry 2020In analytical science, mass spectrometry (MS) is known as a "gold analytical tool" because of its unique character of providing the direct molecular structural... (Review)
Review
In analytical science, mass spectrometry (MS) is known as a "gold analytical tool" because of its unique character of providing the direct molecular structural information of the relevant analyte molecules. Therefore, MS technique has widely been used in all branches of chemistry along with in proteomics, metabolomics, genomics, lipidomics, environmental monitoring etc. Mass spectrometry-based methods are very much needed for fast and reliable detection and quantification of drugs of abuse and explosives in order to provide fingerprint information for criminal investigation as well as for public security and safety at public places, respectively. Most of the compounds exist as their neutral form in nature except proteins, peptides, nucleic acids that are in ionic forms intrinsically. In MS, ion source is the heart of the MS that is used for ionizing the electrically neutral molecules. Performance of MS in terms of sensitivity and selectivity depends mainly on the efficiency of the ionization source. Accordingly, much attention has been paid to develop efficient ion sources for a wide range of compounds. Unfortunately, none of the commercial ion sources can be used for ionization of different types of compounds. Moreover, in MS, analyte molecules must be released into the gaseous phase and then ionize by using a suitable ion source for detection/quantification. Under these circumstances, fabrication of new ambient ion source and ultrasonic cutter blade-based non-thermal and thermal desorption methods have been taken into account. In this paper, challenges and strategies of mass spectrometry analysis of the drugs of abuse and explosives through fabrication of ambient ionization sources and new desorption methods for non-volatile compounds have been described. We will focus the literature progress mostly in the last decade and present our views for the future study.
PubMed: 33537286
DOI: 10.3389/fchem.2020.598487 -
Rapid Communications in Mass... Jan 2021The development of miniaturized and field portable mass spectrometers could not succeed without a simple, compact, and robust ionization source. Here we present a...
RATIONALE
The development of miniaturized and field portable mass spectrometers could not succeed without a simple, compact, and robust ionization source. Here we present a voltage-free ionization method, Vibrating Sharp-edge Spray Ionization (VSSI), which can generate a spray of liquid samples using only one standard microscope glass slide to which a piezoelectric transducer is attached. Compared with existing ambient ionization methods, VSSI eliminates the need for a high electric field (~5000 V·cm ) for spray generation, while sharing a similar level of simplicity and flexibility with the simplest direct ionization techniques currently available such as paper spray ionization (PSI) and other solid substrate-based electrospray ionization methods.
METHODS
The VSSI device was fabricated by attaching a piezoelectric transducer onto a standard glass microscope slide using epoxy glue. Liquid sample was aerosolized by either placing a droplet onto the vibrating edge of the glass slide or touching a wet surface with the glass edge. Mass spectrometric detection was achieved by placing the VSSI device 0.5-1 cm from the inlet of the mass spectrometer (Q-Exactive, ThermoScientific).
RESULTS
VSSI is demonstrated to ionize a diverse array of chemical species, including small organic molecules, carbohydrates, peptides, proteins, and nucleic acids. Preliminary sensitivity experiments show that high-quality mass spectra of acetaminophen can be obtained by consuming 100 femtomoles of the target. The dual spray of VSSI was also demonstrated by performing in-droplet denaturation of ubiquitin. Finally, due to the voltage-free nature and the direct-contact working mode of VSSI, it has been successfully applied for the detection of chemicals directly from human fingertips.
CONCLUSIONS
Overall, we report a compact ionization method based on vibrating sharp-edges. The simplicity and voltage-free nature of VSSI make it an attractive option for field portable applications or analyzing biological samples that are sensitive to high voltage or difficult to access by conventional ionization methods.
PubMed: 29993155
DOI: 10.1002/rcm.8232 -
Essays in Biochemistry Mar 2023This review aims to summarise the current capabilities of surface mass spectrometry (MS) approaches that offer intact protein analysis, and that of non-covalent... (Review)
Review
This review aims to summarise the current capabilities of surface mass spectrometry (MS) approaches that offer intact protein analysis, and that of non-covalent complexes. Protein analysis is largely achieved via matrix-assisted laser desorption/ionisation (MALDI), which is in itself a surface analysis approach or solvent-based electrospray ionisation (ESI). Several surface sampling approaches have been developed based on ESI, and those that have been used for intact protein analysis will be discussed below. The extent of protein coverage, top-down elucidation, and probing of protein structure for native proteins and non-covalent complexes will be discussed for each approach. Strategies for improving protein analysis, ranging from sample preparation, and sampling methods to instrument modifications and the inclusion of ion mobility separation in the workflow will also be discussed. The relative benefits and drawbacks of each approach will be summarised, providing an overview of current capabilities.
Topics: Proteins; Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
PubMed: 36748325
DOI: 10.1042/EBC20220191 -
International Journal of Analytical... 2018Modern technical evolution made mass spectrometry (MS) an absolute must for analytical chemistry in terms of application range, detection limits and speed. When it comes... (Review)
Review
Modern technical evolution made mass spectrometry (MS) an absolute must for analytical chemistry in terms of application range, detection limits and speed. When it comes to mass spectrometric detection, one of the critical steps is to ionize the analyte and bring it into the gas phase. Several ionization techniques were developed for this purpose among which electrospray ionization (ESI) and atmospheric pressure chemical ionization (APCI) are two of the most frequently applied atmospheric pressure methods to ionize target compounds from liquid matrices or solutions. Moreover, recent efforts in the emerging field of "ambient" MS enable the applicability of newly developed atmospheric pressure techniques to solid matrices, greatly simplifying the analysis of samples with MS and anticipating, to ease the required or even leave out any sample preparation and enable analysis at ambient conditions, outside the instrument itself. These developments greatly extend the range of applications of modern mass spectrometry (MS). Ambient methods comprise many techniques; a particular prominent group is, however, the plasma-based methods. Although ambient MS is a rather new field of research, the interest in further developing the corresponding techniques and enhancing their performance is very strong due to their simplicity and often low cost of manufacturing. A precondition for improving the performance of such ion sources is a profound understanding how ionization works and which parameters determine signal response. Therefore, we review relevant compound characteristics for ionization with the two traditional methods ESI and APCI and compare those with one of the most frequently employed representatives of the plasma-based methods, i.e., low temperature plasma ionization. We present a detailed analysis in which compound characteristics are most beneficial for the response of aromatic nitrogen-containing compounds with these three methods and provide evidence that desorption characteristics appear to have the main common, general impact on signal response. In conclusion, our report provides a very useful resource to the optimization of instrumental conditions with respect to most important requirements of the three ionization techniques and, at the same time, for future developments in the field of ambient ionization.
PubMed: 30723503
DOI: 10.1155/2018/5647536 -
Frontiers in Chemistry 2022Strong field ionization of neutral iodoacetylene (HCCI) can produce a coherent superposition of the X and A cations. This superposition results in charge migration...
Strong field ionization of neutral iodoacetylene (HCCI) can produce a coherent superposition of the X and A cations. This superposition results in charge migration between the CC orbital and the iodine -type lone pair which can be monitored by strong field ionization with short, intense probe pulses. Strong field ionization of the X and A states of HCCI cation was simulated with time-dependent configuration interaction using singly ionized configurations and singly excited, singly ionized configurations (TD-CISD-IP) and an absorbing boundary. Studies with static fields were used to obtain the 3-dimensional angular dependence of instantaneous ionization rates by strong fields and the orbitals involved in producing the cations and dications. The frequency of charge oscillation is determined by the energy separation of the X and A states; this separation can change depending on the direction and strength of the field. Furthermore, fields along the molecular axis can cause extensive mixing between the field-free X and A configurations. For coherent superpositions of the X and A states, the charge oscillations are characterized by two frequencies-the driving frequency of the laser field of the probe pulse and the intrinsic frequency due to the energy separation between the X and A states. For linear and circularly polarized pulses, the ionization rates show marked differences that depend on the polarization direction of the pulse, the carrier envelope phase and initial phase of the superposition. Varying the initial phase of the superposition at the beginning of the probe pulse is analogous to changing the delay between the pump and probe pulses. The charge oscillation in the coherent superposition of the X and A states results in maxima and minima in the ionization yield as a function of the superposition phase.
PubMed: 35548678
DOI: 10.3389/fchem.2022.866137 -
The Cochrane Database of Systematic... Sep 2012Previous reports have shown that ion content in the air may have an effect on respiratory function. Results from studies which test the efficacy of air ionisers to... (Review)
Review
BACKGROUND
Previous reports have shown that ion content in the air may have an effect on respiratory function. Results from studies which test the efficacy of air ionisers to reduce asthma symptoms are often inconclusive and their use as a treatment for asthma remains debatable.
OBJECTIVES
We conducted a systematic review of the available evidence to determine the effectiveness of positive and negative ion generators in people with asthma.
SEARCH METHODS
We searched the Cochrane Airways Group Specialised Register, Cochrane Central Register of Controlled Trials (CENTRAL) as well as the alternative medicine database AMED. Searches were current as of June 2012.
SELECTION CRITERIA
Randomised controlled trials (parallel or crossover design studies) comparing ionisers with dummy ionisers (being negative or positive ion emitters), in children or adults with chronic asthma.
DATA COLLECTION AND ANALYSIS
Two reviewers independently assessed titles and abstracts of studies and assessed trial quality. Study quality was determined using two methods:The Cochrane approach to allocation concealment and the five point Jadad scale.
MAIN RESULTS
Six studies were selected for inclusion (106 participants). No results were combined as the studies were all of a crossover design.EFFECTS OF NEGATIVE ION GENERATORS (five studies) No study reported a significant difference in lung function between ionised and control air (morning Peak expiratory flow (PEF) - three studies; forced expiratory flow in one second (FEV1) - one study). There were no significant differences in symptoms or beta-2 agonist usage between ionised and control air in three studies.EFFECTS OF POSITIVE ION GENERATORS (one study) This study demonstrated that although positively ionised air was associated with a larger fall in FEV1 with exercise, this did not reach statistical significance. Baseline FEV1 was not demonstrated to be significantly different between treatment groups.
AUTHORS' CONCLUSIONS
Based on the evidence currently available from randomised controlled trials, a recommendation cannot be given for the use of room air ionisers to reduce symptoms in patients with chronic asthma.
Topics: Adolescent; Adult; Air Ionization; Anions; Asthma; Cations; Child; Child, Preschool; Cross-Over Studies; Humans; Infant; Ions; Randomized Controlled Trials as Topic; Young Adult
PubMed: 22972060
DOI: 10.1002/14651858.CD002986.pub2