Aims/hypothesis To assess thiamine status by analysis of plasma, erythrocytes and urine in type 1 and type 2 diabetic patients and links to markers of vascular dysfunction. Methods Diabetic patients (26 type 1 and 48 type 2) with and without microalbuminuria and 20 normal healthy control volunteers were recruited. Erythrocyte activity of transketolase, the concentrations of thiamine and related phosphorylated metabolites in plasma, erythrocytes and urine, and markers of metabolic control and vascular dysfunction were determined. Results Plasma thiamine concentration was decreased 76% in type 1 diabetic patients and 75% in type 2 diabetic patients: normal volunteers 64.1 (95% CI 58.5-69.7) nmol/l, type 1 diabetes 15.3 (95% CI 11.5-19.1) nmol/l, p< 0.001, and type 2 diabetes 16.3 (95% CI 13.0-9.6) nmol/l, p<0.001. Renal clearance of thiamine was increased 24-fold in type 1 diabetic patients and 16-fold in type 2 diabetic patients. Plasma thiamine concentration correlated negatively with renal clearance of thiamine (r=−0.531, p< 0.001) and fractional excretion of thiamine (r=−0.616, p< 0.001). Erythrocyte transketolase activity correlated negatively with urinary albumin excretion (r=−0.232, p<0.05). Thiamine transporter protein contents of erythrocyte membranes of type 1 and type 2 diabetic patients were increased. Plasma thiamine concentration and urinary excretion of thiamine correlated negatively with soluble vascular adhesion molecule-1 (r=−0.246, p<0.05, and −0.311, p<0.01, respectively). Conclusions/interpretation Low plasma thiamine concentration is prevalent in patients with type 1 and type 2 diabetes, associated with increased thiamine clearance. The conventional assessment of thiamine status was masked by increased thiamine transporter content of erythrocytes.

Although laser desorption mass spectrometry was introduced in the 1960s, the potential of laser mass spectrometry was not realised until the introduction of matrix-assisted laser desorption/ionisation (MALDI) in the 1980s. The technique relies on light-absorbing compounds called matrices that are co-crystallised with the analyte to achieve high ionisation and desorption efficiencies. MALDI offers a lot of advantages and is an indispensable tool in macromolecule analysis. However, the presence of the matrix also produces a high chemical background in the region below m/z 700 in the mass spectrum. Surface-assisted laser desorption/ionisation (SALDI) substitutes the chemical matrix of MALDI for an active surface, which means that matrix interference can be eliminated. SALDI mass spectrometry has evolved in recent years into a technique with great potential to provide insight into many of the challenges faced in modern research, including the growing interest in "omics" and the demands of pharmaceutical science. A great variety of materials have been reported to work in SALDI. Examples include a number of nanomaterials and surfaces. The unique properties of nanomaterials greatly facilitate analyte desorption and ionisation. This article reviews recent advances made in relation to carbon- and semiconductor-based SALDI strategies. Examples of their environmental, chemical and biomedical applications are discussed with the aim of highlighting progression in the field and the robustness of the technique, as well as to evaluate the strengths and weaknesses of individual approaches. In addition, this article describes the physical and chemical processes involved in SALDI and explains how the unique physical and electronic properties of nanostructured surfaces allow them to substitute for the matrix in energy transfer processes.