No abstract

No abstract

We report a bottom‐up synthesis of iron oxide and gold nanoparticles, which are functionalized and combined to form a nanohybrid serving as an immune sensor, which selectively binds to tau protein, a biomarker for diagnosis of Alzheimer's disease. Detection of the target analyte is achieved by surface‐enhanced Raman scattering originating from the diagnostic part of the nanohybrid that was prepared from Au nanoparticles functionalized with 5,5′‐dithiobis‐(2‐nitrobenzoic acid) as a Raman reporter and monoclonal anti‐tau antibody. The magnetic part consists of FexOy nanoparticles functionalized with polyclonal anti‐tau antibody and is capable to separate tau protein from a complex matrix such as cerebrospinal fluid. We further identified and validated a set of analytical tools that allow monitoring the success of both nanoparticle preparation and each functionalization step performed during the assembly of the two binding sites by an immune reaction. By applying UV/Vis spectroscopy, dynamic light scattering, zeta potential measurements, X‐ray diffraction, small‐angle X‐ray scattering, and transmission electron microscopy, we demonstrate a proof‐of‐concept for a controlled and step‐by‐step traceable synthesis of a tau protein‐specific immune sensor.

Triple isotope dilution mass spectrometry (triple IDMS) has been applied for the first time on protein quantification, especially on transferrin. Transferrin as an acute phase protein is a marker for several inflammation processes in the human body. Therefore, in Germany, the accurate and precise measurement of this important analyte is required. In this work, a new approach to triple IDMS is described and compared to double IDMS. Also, complete uncertainty budgets for both methods were set up to demonstrate the ability of this method to be used as a reference procedure. The relative expanded uncertainty (k=2) for triple IDMS (3.6 %) is smaller than the one for double IDMS (4.0 %). The content of transferrin found in the human serum reference material ERM-DA470k/IFCC ((2.41±0.08) g/kg) with both methods was in good agreement with each other and with the certificate. For triple IDMS ((2.426±0.086) g/kg) and for double IDMS ((2.317±0.092) g/kg), transferrin was determined. Although triple IDMS is a little more time consuming compared to double IDMS, there is the advantage that the isotopic composition of the spike material does not have to be determined. This is very useful especially in case of a marginal isotopic enrichment in the spike or problems with the accurate measurement of the spike isotope ratio.

The total haemoglobin (Hb) concentration in blood is one of the most frequently measured analytes in clinical medicine because of its significance for evaluating the health state of a human. The spectrophotometric cyanmethaemoglobin (HiCN) method is the internationally accepted conventional reference method to determine this biomarker. It is frequently used in clinical routine diagnostics but is not traceable to the International System of Units and thus does not meet highest metrological demands. A further critical issue is the toxicity of the necessary potassium cyanide. Different methods to solve these problems are reported here. They all were validated against the HiCN method in an interlaboratory comparison by measuring the total Hb concentration present in the certified reference material JCCRM 912-2M. Methods considered were the spectrophotometric alkaline haematin detergent (AHD) method as well as several isotope dilution (ID)-based approaches. The latter include inductively coupled plasma mass spectrometry (ICP-MS), species-specific (SS) ICP-MS, organic MS and Raman spectrometry. Graphical abstract ᅟ.