New mass spectrometry innovations are helping overcome various issues. Acoustic sampling, for example, is enabling thousands of measurements to be made every hour with minimal or no sample preparation.
Mass spectrometry (MS) is a widely used technique for food safety, environmental, pharmaceutical, biological, and forensic investigations where the simultaneous detection of targeted and non-targeted compounds is of pivotal importance. A plethora of analytical MS methods, also coupled to different separation techniques such as gas- and liquid-chromatography and their multidimensional analogues or capillary electrophoresis, have been developed and validated in order to analyze complex matrices. However, despite the rapid evolution from its beginning, the development of online and real-time analytical MS methodologies, especially ambient ionization methods, is strongly demanded to perform high-throughput analysis and to obtain highly informative spectra. In this context, novel materials and instrumental configurations are under study to enhance the performance of different instruments, whereas powerful, high-resolution mass spectrometers are required to univocally identify targeted compounds. Finally, libraries of compounds, including MS-based information, such as accurate mass, isotopic patterns, and collision-induced fragmentation, are strongly demanded together with studies regarding the establishment of recognized analytical performance criteria to assess the occurrence of residues in the environment. Mass spectrometric imaging is another emerging powerful analytical technique that can be applied to perform analyses of multiple molecules in complex samples without labeling, thus providing a distinct advantage over preexisting methods for label-free and simultaneous detection of drugs and metabolites.
While the traditional coupling of MS with liquid chromatography (LC) and gas chromatography (GC) continues to be a robust method, technological advances have seen the rise of other techniques, such as matrix-assisted laser desorption (MALDI), being directly coupled with MS, making it adept for even more applications. For example, the latest MS technologies can simultaneously analyze many features in one cell, which could help researchers discover novel targets with the potential for translation into new therapies. Today, biotherapeutic products account for a growing proportion of new drug approvals. Increased focus on the development of much larger, more complex therapeutics, such as monoclonal antibodies, fusion proteins, and antibody-drug conjugates, has placed new demands on mass spectrometry. While small-molecule drugs can easily be analyzed on a system with a mass range of 1250 Dalton (Da), the analysis of higher-order structures, such as peptides, proteins, and oligonucleotides, can require the visualization of ions from the 2000-Da to the tens of thousands of Da range.
This increased molecular complexity means that much greater instrument resolution is required to confidently elucidate atomic-level structure and function. Where a single or triple-quadrupole mass spectrometer offering unit-mass resolution may be sufficient for early metabolite, impurity, and degradant screening, high-resolution accurate mass (HRAM) has become increasingly important for the analysis of large biotherapeutics and protein complexes.
The evolution of mass analyzers to acquire high-resolution data at high-mass ranges, in time frames amenable to coupling with ultra-high-performance LC (UHPLC) has been incredibly important for drug discovery efforts. The commercialization of mass spectrometers with high mass, high-resolving capabilities has undoubtedly opened new avenues in the study of protein drugs and their targets. Historically the coupling of these techniques was only possible via offline LC separations from which fractions were collected for subsequent static nanospray HRAM MS analysis. Through direct combination of native protein chromatographic separations and HRAM detection, researchers now have at their disposal the possibility of automated, high-throughput native intact mass analysis of complex therapeutics and drug targets/complexes.
While advances in mass range and resolution are generating ever more powerful insights, sample preparation is still a major challenge, especially for bioanalysis applications. Currently, many MS workflows rely on expert users to prepare samples, which can be the rate-limiting step in many drug discovery workflows.
Although there are kits available that can reduce preparation time for some samples from days to hours, introducing new ways of working that simplify or bypass these complex processes is still a key priority for many developers of MS products.
New MS innovations are helping to overcome this issue. Acoustic sampling, for example, is enabling thousands of measurements to be made every hour with minimal to no sample preparation. As a result, this is allowing high-throughput screens or activity assays to be developed. Moreover, the implementation of direct MS analysis, based on ambient ionization techniques, such as direct analysis in real time (DART) and desorption electrospray ionization (DESI), is further simplifying bioanalysis workflows. Because these techniques can operate in the open-laboratory environment, they do not require sample pre-treatment steps – streamlining workflows and enabling researchers to collect more data, faster.
Additionally, as many new, powerful MS technologies can directly analyze substrates, without reagents, fewer artifacts are generated, which in turn increases confidence in results. Not only does better data quality aid researchers with their drug discovery efforts, but the costs saved on reagents can be reinvested to help expedite other parts of the pipeline. For instance, using the funds to perform more large-scale compound screens could help to identify more chemical starting points and so increase the potential of drug discovery success.
These technologies are beginning to remove barriers that can increase timelines, not only for high-value activities, such as tissue imaging, but also for purity assessment and confirmation of identity in medicinal chemistry synthesis. With the average time to market for most therapies being around a decade (and costing upwards of USD 1 billion), innovations such as these are playing an important role in accelerating the delivery of new therapies to the patients who need them.
Differential mobility spectrometry (DMS) has proven to be a valuable addition to ion mobility spectrometry methods, providing separations that are orthogonal to traditional LC-MS workflows. The technique makes use of a fast gas stream at right angles to an electric field, which causes ions of different mobilities to pass through the instrument with different trajectories.
The use of DMS can sometimes circumvent the need to use LC techniques, due to its ability to provide reduced isobaric and isomeric chemical noise, without the need for extensive sample preparation steps. As a result, it is considered to be a powerful approach for bioanalysis workflows.
CE-MS is a powerful analytical technique that combines the high separation efficiency of capillary electrophoresis with detailed characterization that can be achieved using MS or HRAM analysis. As the method allows the analysis of intact proteins and various small molecules, including peptides, CE-MS is helping researchers obtain answers to questions that would not otherwise be possible using conventional LC techniques.
The road ahead
Improvements in sensitivity, precision, and accuracy of instruments for research purposes have largely driven the remarkable advances in instrument design that have taken place over the last decade. However, with biotherapeutics set to play an even greater role in the future of medicine, developers of MS technologies are increasingly looking to better meet the needs of biopharma discovery workflows. Here, there is a clear focus on automation, miniaturization, and making both instruments and analysis software user-friendly.
In the future, one should expect to see greater use of miniaturized systems that can be implemented directly into automated drug synthesis and testing processes. Direct-ionization techniques are also likely to mature from the early research-focused products to more mainstream solutions geared toward non-expert users. With mass spectrometry becoming more widely used in drug discovery, the requirement for user-friendly technologies that meet the needs of non-mass spectrometry specialists does not simply relate to instruments themselves. The analysis workflows and software used to control them is also set to become increasingly accessible and here, computer algorithms are likely to take up the slack.
One of the biggest changes expected over the next 3 to 5 years is the incorporation of artificial intelligence into MS data analysis, enabling the searching of not only well-organized databases but also external data, such as journal text. This will greatly increase knowledge generation from MS data sources. MS has long been a valuable tool in the drug discovery toolbox; however, recent advances are set to open up an array of new opportunities for biopharmaceutical developers and patients alike. The ability to combine increasingly powerful MS analysis with orthogonal techniques, such as capillary electrophoresis, SEC, and IEX is allowing researchers to obtain answers to questions that would otherwise not be possible using traditional separation methods.
Moreover, the latest MS tools are helping to minimize or even eliminate the complex sample preparation steps that are a current bottleneck in many MS workflows. By providing researchers with effective solutions, these technologies are helping to accelerate the delivery of safe and effective biotherapeutics to patients.