Enrichment of phospholipids using magnetic Fe3O4/TiO2 nanoparticles for quantitative detection at single cell levels by electrospray ionization mass spectrometry

Coupling Miniaturized Stir Bar Sorptive Dispersive Microextraction to Needle-Based Electrospray Ionization Emitters for Mass Spectrometry: Determination of Tetrahydrocannabinol in Human Saliva as a Proof of Concept

Direct coupling of sample preparation with mass spectrometry (MS) can speed up analysis, enabling faster decision-making. In such combinations, where the analysis time is mainly defined by the extraction procedure, magnetic dispersive solid-phase extraction emerges as a relevant technique because of its rapid workflow. The dispersion and retrieval of the magnetic sorbent are typically uncoupled stages, thus reducing the potential simplicity. Stir bar sorptive dispersive microextraction (SBSDME) is a novel technique that integrates both stages into a single device. Its miniaturization (mSBSDME) makes it more portable and compatible with low-availability samples. This article reports the direct combination of mSBSDME and MS using a needle-based electrospray ionization (NESI) emitter as the interface. This combination is applied to determine tetrahydrocannabinol in saliva samples, a relevant societal problem if the global consumption rates of cannabis are considered. The coupling requires only the transference of the magnet (containing the sorbent and the isolated analyte) from the mSBSDME to the hub of a hypodermic needle, where the online elution occurs. The application of 5 kV on the needle forms an electrospray on its tip, transferring the ionized analyte to the MS inlet. The excellent performance of mSBSDME-NESI-MS/MS relies on the sensitivity (limits of detection as low as 2.25 ng mL-1), the precision (relative standard deviation lower than 15%), and the accuracy (relative recoveries ranged from 87 to 127%) obtained. According to the results, the mSBSDME-NESI-MS/MS technique promises faster and more efficient chemical analysis in MS-based applications.

Investigating the Metabolic Heterogeneity of Cancer Cells Using Functional Single-Cell Selection and nLC Combined with Multinozzle Emitter Mass Spectrometry

Tumor metastasis and cancer recurrence are often a result of cell heterogeneity, where specific subpopulations of tumor cells may be resistant to radio- or chemotherapy. To investigate this physiological and phenotypic diversity, single-cell metabolomics provides a powerful approach at the chemical level, where distinct lipid profiles can be found in different tumor cells. Here, we established a highly sensitive platform using nanoflow liquid chromatography (nLC) combined with multinozzle emitter electrospray ionization mass spectrometry for more in-depth metabolomics profiling. Our platform identified 15 and 17 lipids from individual osteosarcoma (U2OS) and glioblastoma (GBM) cells when analyzing single-cell samples. Additionally, we used the functional single-cell selection (fSCS) pipeline to analyze the subpopulations of cells with a DNA damage response (DDR) in U2OS cells and fast migration in GBM cells. Specifically, we observed a down-regulation of polyunsaturated fatty acids (PUFAs) in U2OS cells undergoing DDR, such as fatty acids FA 20:3; O2 and FA 17:4; O3. Furthermore, ceramides (Cer 38:0; O3) and triglycerides (TG 36:0) were found to be down-regulated in fast-migrating GBM cells compared to the slow-migrating subpopulation. These findings suggest the potential roles of these metabolites and/or lipids in the cellular behavior of the subpopulations.

Selective extraction of phospholipids from human milk using glass fabric modified with zirconium-based metal organic framework

Phospholipids (PLs) are important and complex trace lipids in milk, which have positive effects on the infants' nervous and immune system development. Herein, a new method for selective extraction of PLs using glass fabric @ MOF-808 was proposed. Based on Lewis acid-base interaction, MOF-808 containing abundant Zr-OH groups was selected as the adsorption body, and glass fabric was used as a substrate to make the adsorbent easy to remove and reuse. The influencing factors such as loading solution, extraction time, eluent and elution time were further investigated. The adsorbent showed high adsorption capacity (3.31-6.54 mg/g for PLs) and good reusability (reused at least five times). The method showed low detection limits (1.61 μg/L - 10.24 μg/L) and quantification limits (5.24 μg/L-51.21 μg/L) for eight classes of PLs. The analysis of PLs in human milk at different lactation stages by ultra-high performance liquid chromatography-quadrupole time-of-flight mass spectrometry could obtain up to 206 PLs, indicating that the method has extremely high extraction and anti-interference capabilities. This work is the first time to introduce MOF materials to selectively extract PLs and use glass fabric as a substrate for MOF-808, which has the advantages of easy recovery and high sensitivity. It provides technical support for the discovery of more PL species and has potential applications in phospholipidomics.

TiO2@COF-based solid-phase microextraction combined with UHPLC-MS/MS for the rapid determination of potential biomarkers of phosphatidylcholines and lysophosphatidylcholines in head and neck cancers

Phosphatidylcholine (PC) and lysophosphatidylcholine (LPC), two types of phospholipids (PLs), have been reported to be closely correlated with head and neck cancers of laryngeal cancer (LC) and thyroid cancer (TC), which make their analysis crucial. TiO2@COF-based solid-phase microextraction (SPME) coupled to UHPLC-MS/MS was developed for the rapid and accurate detection of seven potential PL biomarkers from small amounts of serum in this work. The combination of TiO2 and COF proves to be effective for the extraction of the target analytes. Under optimal conditions, the developed TiO2@COF-based SPME-UHPLC-MS/MS method revealed good linearity (R2 ≥ 0.997) with LODs ranging from 0.05 to 0.38 ng/mL for PLs, the extraction recoveries and matrix effects ranging from 83.09-112.03% and 85.38-113.67%, respectively. As a high-throughput pretreatment method, satisfactory probe-to-probe reproducibility rates of 2.7-10.1% were obtained. Finally, the TiO2@COF-based SPME-UHPLC-MS/MS method was applied to analyze LPC 14:0, LPC 16:0, LPC 18:0, LPC 18:1, LPC 19:0, PC 16:0/18:1, and PC 18:0 in serum samples from early LC patients (n = 15), early TC patients (n = 15), and healthy volunteers (n = 15). The results indicated that cancer patients could be effectively differentiated from healthy controls using orthogonal partial least squares discriminant analysis (OPLS-DA). In conclusion, the established TiO2@COF-based SPME-UHPLC-MS/MS method is reliable for the rapid determination of the seven PLs in serum samples, which is promising for early diagnosis of head and neck cancers.

Analytical Techniques for Single-Cell Biochemical Assays of Lipids

Lipids are essential cellular components forming membranes, serving as energy reserves, and acting as chemical messengers. Dysfunction in lipid metabolism and signaling is associated with a wide range of diseases including cancer and autoimmunity. Heterogeneity in cell behavior including lipid signaling is increasingly recognized as a driver of disease and drug resistance. This diversity in cellular responses as well as the roles of lipids in health and disease drive the need to quantify lipids within single cells. Single-cell lipid assays are challenging due to the small size of cells (∼1 pL) and the large numbers of lipid species present at concentrations spanning orders of magnitude. A growing number of methodologies enable assay of large numbers of lipid analytes, perform high-resolution spatial measurements, or permit highly sensitive lipid assays in single cells. Covered in this review are mass spectrometry, Raman imaging, and fluorescence-based assays including microscopy and microseparations.

PDMS-TiO2 composite films combined with LC-MS/MS for determination of phospholipids of urine in non-small cell lung cancer patients with traditional Chinese medicine syndromes

Lung cancer is one of the most common malignant tumors in China. Most patients are already in the mid to advanced stages during the consultation and the survival rate is less than 23 % with a poor prognosis. Therefore, effective dialectical diagnosis of advanced cancer can guide individualized treatment to improve survival. Phospholipids are the building blocks of cell membranes and abnormal phospholipid metabolism is associated with plentiful diseases. Most studies of disease markers use blood as a sample. However, urine covers extensive metabolites that are produced during the body's metabolic processes. Therefore, the study of markers in urine can be used as a complement to improve the diagnosis rate of marker diseases. Moreover, urine is characterized by high water content, high polarity, and high inorganic salt, therefore the detection of phospholipids in urine is challenging. In this study, an original Polydimethylsiloxane (PDMS)-titanium dioxide (TiO₂) composite film for sample pre-treatment coupled with the LC-MS/MS method for the determination of phospholipids in the urine with high selectivity and low matrix effects was prepared and developed. The extraction process was scientifically optimized by the single-factor test. After systematic validation, the established method was successfully applied to the accurate determination of phospholipid substances in the urine of lung cancer patients and healthy subjects. In conclusion, the developed method has great potential for the development of lipid enrichment analysis in urine and can be used as a beneficial tool for cancer diagnosis and Chinese medicine syndrome typing.

MG@PD@TiO2 nanocomposite based magnetic solid phase extraction coupled with LC-MS/MS for determination of lysophosphatidylcholines biomarkers of plasma in psoriasis patients

Lysophosphatidylcholine (LPC) was commonly known as a class of significant differential metabolites of high relevance with many diseases including psoriasis, of which the accurate determination is of great importance to diagnosis or prediction to many diseases. However, it is challenging and complicated because of the enormous biological sample complexity and impurities interference. In this study, we synthesized a magnetic nanocomposite MG@PD@TiO₂ and took advantage of the interactions of Lewis acid-base between the phosphate groups in LPCs and Ti ions on MG@PD@TiO₂ nanomaterials for selective separation and enrichment of LPCs from complex biological matrix. The solid-phase extraction sample pretreatment process by means of MG@PD@TiO₂ nanomaterials coupled with LC-MS/MS method was then applied to actual determination of six typical LPCs (LPC 10:0, 14:0, 16:0, 18:0, 18:1, 22:0) in human plasma. The extraction conditions were scientifically optimized by single-factor test (adsorbent amount, adsorption and desorption time, elution solvent type, eluant volume). Under the optimal conditions, the detection limits (LOD, S/N = 3) and quantification limits (LOQ, S/N = 10) were 1 and 5 ng/mL for LPC 10:0 and LPC 14:0, 0.02 and 0.1 ng/mL for LPC 16:0 and LPC 18:1, 0.05 and 0.2 ng/mL LPC 18:0 and LPC 22:0, respectively. The intra- and inter-day precisions were 3.82-12.60 % (n = 6) and 3.29-13.50 % (n = 6) respectively, the recoveries were in the range of 91.92-113.69 % and the stability of the analytes in the matrix performed well with RSDs≤15.51 %. Finally, the developed method was successfully applied to the accurate determination of six LPCs biomarkers of plasma in patients with psoriasis (n = 10) and control groups (n = 10).

Lipidomics phenotyping of clam (Corbicula fluminea) through graphene/fibrous silica nanohybrids based solid-phase extraction and HILIC-MS analysis

Polyunsaturated phospholipids are abundant in clam (Corbicula fluminea) but difficult to be fully extracted. Herein, graphene/fibrous silica (G/KCC-1) nanohybrids were synthesized, characterized, and applied for solid-phase extraction (SPE) of phospholipids in clam. The effectiveness of G/KCC-1 SPE was verified by hydrophilic interaction chromatography mass spectrometry (HILIC-MS) based lipidomics and statistical analysis. The ions of PE 16:0/18:1 (m/z 716.4), PC 16:0/20:5 (m/z 824.6) and etc. were regarded as the main difference among the crude lipids, acetone washed extract, and eluate of G/KCC-1 SPE. Finally, this method was validated in terms of linearity (R² 0.9965 to 0.9981), sensitivity (LOD 0.19-0.51 μg·mL^-1 and LOQ 0.48 - 1.47 μg·mL^-1), and precision (RSD_intra-day ≤ 7.16% and RSD_inter-day ≤ 7.30%). In conclusion, the G/KCC-1 SPE and HILIC-MS method was shown to be accurate and efficient in selective extracting and phenotyping phospholipids in C. fluminea.

Recent development of nanoparticle-assisted metabolites analysis with mass spectrometry

Metabolomics systematically studies the changes of metabolites in biological systems in the temporal or spatial dimensions. It is a challenging task for comprehensive analysis of metabolomics because of diverse physicochemical properties and wide concentration distribution of metabolites. Used as enrichment sorbents, chemoselective probes, chromatographic stationary phases, MS ionization matrix, nanomaterials play excellent roles in improving the selectivity, separation performance, detection sensitivity and identification efficiency of metabolites when mass spectrometry is employed as the detection technique. This review summarized the recent development of nanoparticle-assisted metabolites analysis in terms of assisting the pretreatment of biological samples, improving the separation performance and enhancing the MALDI-MS detection.

Nano-optosensor based on titanium dioxide and graphene quantum dots composited with specific polymer for cefazolin detection

An optosensor using nanocomposite probes was fabricated for the detection of trace cefazolin. The nanoprobes utilized the high affinity of titanium dioxide, the good optical properties of graphene quantum dots and the good selectivity of molecularly imprinted polymer. The integration of these materials produced a rapid, highly sensitive optosensor with excellent selectivity for cefazolin detection. The fluorescence intensity of the nanocomposite probes was quenched when cefazolin re-bound with the imprinted recognition cavities of the nanoprobes. The fabricated nanoprobe exhibited a good linearity for cefazolin from 0.10 to 10.0 μg L^-1 with a limit of detection of 0.10 μg L^-1. The imprinting factor of the nanoprobe was 10.6 and selectivity for cefazolin was not affected by the analogue structures of cephalexin, cefatriaxone, cephradine, cefaperazone and ceftazidime. This nano-optosensor probe successfully detected cefazolin in milk and recoveries were between 85.0 and 97.4 % with RSDs less than 5.0 %. The results of analysis with nano-optosensor were in good agreement with HPLC analysis. The fabrication strategy of the nanocomposite probe can be modified for the measurement of other toxic compounds.