Look What You Missed… With Michael Lämmerhofer
Pandemic perseverance, conference cancellations, 2DLC, and lipidomics
We just “celebrated” (at a distance) the second anniversary of the COVID-19 pandemic. Hard to believe that we are now more than two years in – partially paralyzed, but always in hope that it will be over soon.
Luckily, our research labs stayed open throughout, with MS instruments running 24/7. I was in the office every (work)day – though we did try to avoid overcrowding. I have to thank my coworkers for their unlimited motivation and fearlessness. The most deleterious effects were on our group’s social activities (PhD thesis defenses without a physical audience and subsequent celebrations felt strange and incomplete) and on teaching, which was mostly digital, like everywhere else. By the winter of 2021/2022, we had resumed in-person labs (with reduced occupation), but lectures were still digital (synchronous or asynchronous according to the professor’s preference). As of today, the situation is largely back to normal (let’s hope it stays that way).
Overall, our research activities weren’t affected too much during the pandemic, and, fortunately, we had very few infections within the group. But as a conference organizer, things were a little different.
In 2016, we made a successful bid for HPLC 2021 in Düsseldorf, Germany – which feels like a decade ago. We made an early decision to postpone for two years, which was accepted by the PSC, Gert Desmet (the chairman of the next European HPLC after Düsseldorf, now in 2025), and the Congress Center Düsseldorf, which allowed postponement at no extra cost. We are optimistic about the prospect of a standard symposium in 2023, with a high-quality scientific program, a social program that gives us the opportunity to have stimulating discussions with friends and colleagues, and a big exhibition with all the major vendors and suppliers participating and showcasing their latest developments. And I’m sure that’s what we’ll see at this year’s San Diego meeting.
I think we all missed the discussions, stimulating presentations, input and atmosphere at HPLC, which have always been at the forefront of separation science – many of the revolutionary developments in liquid chromatography were first presented at HPLC meetings. Let’s see what we learn this year.
My HPLC2022 Talk
My talk will be the closing plenary session, for which I selected the topic of column coupling and multidimensional liquid chromatography (MDLC). With new robust equipment and exceptional choices of new columns now available, MDLC offers a lot of flexibility in pharmaceutical analysis. We use it a lot, particularly for impurity profiling, where orthogonal selectivities are key to avoid missing relevant impurities. New pharmaceutical modalities, like oligonucleotide drugs, are associated with more complex impurity profiles; and establishing them requires advanced separation technologies, such as 2DLC.
Fast UHPLC separation technology and instrumentation – with small dwell and extra-column volumes – are opening up new opportunities; for example, faster separation in the second dimension. Unfortunately, not in the ms-time scale, like with ion-mobility spectrometry (IMS). However, IMS separates ions by their gas phase property (differences in collisional cross section), which is intrinsic to the analyte, meaning there is less flexibility to “manipulate” selectivity by experimental factors. In LC, we can modulate selectivity using solvents (including pH and ionic strength) and stationary phase chemistry, so we have more factors to adjust selectivity, but at the expense of analysis time. Though LC separations in sub-second time scales have been shown, they cannot be routinely achieved in practice. We must therefore currently live with sub-minute second dimension separations in 2DLC.
Fully comprehensive 2DLC brings advanced information for complex impurity profiles, where separation in two-dimension is required. And impurity profiles in the form of 2D-contour plots are illustrative images of the quality of drug products.
My main aim will be to present applications from the pharmaceutical analysis field comprising therapeutic peptides, oligonucleotide therapeutics, and stereoisomer separation problems, thus documenting the remarkable feasibility of 2DLC.
Outlook
Looking to the future of our research, we are further advancing our lipidomics pipeline, focusing on extending the coverage of problematic lipids (for example, phosphatidylinositolphosphates, acyl-CoAs) (1, 2) and improving the reliability of identification, while also advancing quantification strategies. The interest in lipidomics analysis from biomedical researchers is steadily increasing, which means more samples and more automation needed.
Our flagship research project is on clinical platelet lipidomics with the University of Tübingen’s cardiology department. Currently, we’re measuring the platelet lipidome of a large cohort of patients suffering from cardiovascular diseases. A variety of mediators of platelet activation are lipids, and platelet activation during thrombotic events involves an instant remodeling of the platelet lipidome. Although these anuclear cellular blood constituents are in contact with plasma, platelets are a compartment with a proprietary lipidome that is specifically processed after a variety of triggers. Platelets are also major drivers of thrombo-inflammation, mediated by a variety of autocrine and paracrine lipid mediators, and are essential components of the immune system. And though antiplatelet therapy has made great progress, it does significantly increase the risk of bleeding events. In other words, there is a need for improved therapies, which lipidomics can assist with by supporting the search for new targets and drugs with platelet inhibitory activity, as we recently showed in a publication (3). The goal is to increase the number of identified lipids in this compartment of the platelet lipidome. Currently, we can identify around 900 platelet lipids in a typical clinical cohort, but this is just a fraction of what’s needed. Quantification is another problem to work on; and improvements are needed in all steps of the workflow. There’s still a lot to do!
On the events side, organizing HPLC 2023 in Düsseldorf, Germany, will be my next big project. After two years of starvation, researchers are keen to exchange their ideas with colleagues and have personal discussions – not just via digital platforms. My calendar is fully packed for this year, which is (hopefully) a good sign that we’ll be all set for next year’s event.
Thematically, we will have a strong focus on hyphenated techniques, biopharmaceuticals, oligonucleotide therapeutics, ion mobility mass spectrometry, fundamentals in separations science, column technologies, and many more hot topics in analytical chemistry. For students, we have already fixed an extended diverse course program with hot topics like 3D-printing, data processing, mass spectrometry advances, 2D-LC, ion mobility spectrometry, and much more. We expect it to be a lively, stimulating meeting in the long tradition of excellent HPLC symposia. We hope many will join!
Michael Lämmerhofer is a Professor at the Institute of Pharmaceutical Sciences, University of Tübingen, Germany
