The 49th Annual Meeting of the Japanese Society for Biomedical Mass Spectrometry (JSBMS) featured the 3rd International Joint Symposium with Mass Spectrometry: Applications to the Clinical Lab (MSACL), marking the first in-person collaboration. Dr. Arash Zarrine-Afsar, Department of Medical Biophysics, University of Toronto, presented “10-Second Cancer Diagnosis with Picosecond Infrared Laser Mass Spectrometry (PIRL-MS),” highlighting PIRL-MS technology. This method combines two innovations: PIRL-DIVE (picosecond infrared laser ablation/desorption by impulsive vibrational excitation) for precise biomolecule extraction and ion detection without conventional sources for minimally invasive diagnostics. The PIRL-MS enables intact biomolecule analysis, tissue classification, and cancer biomarker detection with minimal tissue damage. These advancements make the PIRL-MS a promising intraoperative diagnostics and biomedical research tool. This mini-review focuses on the evolution of his method and briefly summarizes the discoveries and applications that led to this method.

Current newborn screening (NBS) in Japan detects homocystinuria type 1 by elevated levels of methionine (Met), which is insufficient to detect homocystinuria types 2 and 3 that are associated with hypomethioninemia. We have conducted a pilot NBS for inborn errors of cobalamin metabolism in Hiroshima area of Japan since 2018, using the ratio of propionylcarnitine (C3) to Met (C3/Met) and low Met level as markers. We found a newborn female with low Met (9.54 μmol/L, cutoff <10 μmol/L) without elevated C3 or C3/Met in a dried blood specimen collected 4 days post-birth. Second-tier tests revealed slightly elevated total homocysteine (tHcy) (15.7 μmol/L, cutoff ≥5.0 μmol/L) but normal methylmalonic acid (MMA) levels. At 20 days of age, plasma tHcy rose to 52.0 μmol/L, with slightly elevated MMA (3.9 μmol/L, cutoff ≥1.0 μmol/L) and decreased serum vitamin B₁₂ (VB₁₂: 146 pg/mL, reference range 197–771 pg/mL). Gene panel analysis of related disorders detected two MTHFR variants: p.G149V (c. 447delinsTT) and p.P65 L (c.193T>C). 5,10-methylenetetrahydrofolate reductase (MTHFR) activity in lymphocytes and in a dried blood specimen were 56.27 μU/mg protein (8.40% of mean control value) and 50.19 mmol/min/L (11.5% of mean control value), respectively. On the basis of a diagnosis of MTHFR deficiency associated with mild VB₁₂ deficiency, we initiated betaine and mecobalamin administration. The successful detection of this mild case of MTHFR deficiency suggests a good sensitivity of our pilot NBS for the disease, while the combination of second-tier tHcy and MMA measurements is required to retain an appropriate level of specificity.

We previously reported a novel method for isolating extracellular vesicles (EVs) using a polyamine solution through liquid chromatography-tandem mass spectrometry analysis of the culture supernatant of adherent cells, NCI-N87, and demonstrated its efficacy from multiple perspectives. Herein, K562 cells, a suspension cell line, were used to investigate the differences between the adherent cells. Furthermore, we elucidated the mechanism of EV isolation by focusing on the proteins’ isoelectric point (pI) on the EV surface.

Samples were prepared using a conditioned medium from the NCI-N87 and K562 cell lines. The conditioned medium was analyzed after replacing the medium with a serum-free medium and culturing for 48 h. The polyamine precipitation (PA) method was compared with the ultracentrifugation (UC) method.

Using K562 cells, the recovery of EVs using the PA method allowed the detection of common EV marker proteins. The gene ontology analysis also indicated that EV-related terms ranked the highest, similar to the UC method. These results demonstrate that the PA method is also effective for recovering EVs from suspended cells, such as K562 cells.

When the average pI values were calculated with the abundance and the pI values for the surface proteins in the collected EVs, the values with the PA method were lower than those with the UC method. These results suggest that electrostatic interactions bring the easy recovery of EVs with polyamines.

We report a rare case of keratoconjunctivitis in a young Japanese man rapidly identified as Neisseria meningitidis by MALDI-TOF MS (matrix-assisted laser desorption-ionization time-of-flight mass spectrometry). The patient was diagnosed with primary meningococcal conjunctivitis. A 26-year-old man presented to Osaka Medical and Pharmaceutical University with a 3-day history of sudden pain onset in both eyes, conjunctival redness, tearing, and purulent eye discharge. The bulbar and palpebral conjunctiva were hyperemic and thickened, with superficial punctate keratitis in both eyes, and an area of stromal infiltration in the left eye. No epithelial defects or corneal thinning were observed. He had a slight fever and fatigue. Initial Gram staining of the conjunctiva revealed gram-negative diplococci, and, he had a sexual encounter two weeks ago, therefore, we suspected gonococcal conjunctivitis. The patient was administered with 1 g of intravenous ceftriaxone every 12 h for 7 days, and topical cefmenoxime hydrochloride and topical gatifloxacin hydrate were administered eight times per day. His condition improved dramatically after treatment; however, on the third day after admission, Neisseria meningitidis was detected through conjunctival swab culture and biochemical testing using the VITEK^Ⓡ2 NH card. We also rapidly identified Neisseria meningitidis through conjunctival swab mass spectrometry using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). Later, the same bacterium was detected through genetic analyses. Following advice from our hospital’s infectious disease control office, our patient was isolated in a private room for 1 week, and individuals who were in close contact with him were administered ciprofloxacin tablets. We strongly suspected gonococcal infection and initiated treatment, but Neisseria meningitidis was rapidly identified using conjunctival swab MALDI-TOF MS analysis. Therefore, appropriate treatment and infection prevention measures were possible.