A dual-modality immunosensor for simple and reliable detection of nitrated alpha-synuclein in serum based on silver-coated MOF.

Nitrated α-syn (nitro-α-syn) is a biomarker for Parkinson's desease (PD), and its sensitive detection in serum is of great importance for early PD diagnosis. Silver-coated copper MOF (Cu-MOF@Ag) with outstanding oxidase activity and electrochemical response property was designed and synthesized. Cu-MOF@Ag exhibited excellent oxidase activity with a low Km value (0.568 mM), avoiding the addition of strong oxidant to catalyze chromogenic substrate, which enhanced the colorimetric stability. Silver nanoparticles as an electrochemical signal reporter can be easily decorated on the surface of Cu-MOF with bifunctional groups (-SH and -NH2) material, which can increase the electrochemical signal output. The α-syn antibody modified Cu-MOF@Ag and nitro-α-syn modified magnetic nanoparticle were used as immunoprobes to specifically capture nitro-α-syn. A dual-modal immunosensor was fabricated for the simple and reliable detection of nitro-α-syn based on Cu-MOF@Ag. Combing colorimetric and electrochemical detection, nitro-α-syn can be determined quantitatively within a wide linear range (10-350 ng/mL) with low detection limit (0.5 ng/mL). The ability of the sensor with magnetic separation and dual signal analysis allowed to successfully detect nitro-α-syn and distinguish PD patients from healthy people (P < 0.005). Thanks to its excellent selectivity, stability, and the precision of 2.69%, the dual-modal sensor has potential clinical application for nitro-α-syn detection and paves a new way for PD diagnosis at its early stage.

Nanozyme-based cascade SPR signal amplification for immunosensing of nitrated alpha-synuclein.

A self-assembled nanozyme of iron porphyrin mediated supramolecular modified gold nanoparticles (FpA) was fabricated to determine nitrated alpha-synuclein as the Tyr 39 residue (nT39 α-Syn) of a potential biomarker for early diagnosis of Parkinson's disease (PD). Mechanically, localized surface plasmon resonance (LSPR) and the mass effect caused by catalytic deposition of the nanozyme contributed to a cascade signal amplification strategy. The sensor allowed a signal amplification and selective nT39 α-Syn bioanalysis with a 1.34-fold enhancement by cascade amplified SPR signal and double specific recognition. The detection limit was 1.78 ng/mL in the detection range of 7-240 ng/mL. Benefiting from the excellent immunosensor, this method can distinguish healthy people and PD patients using actual samples. Overall, this strategy provides a nanozyme-based biosensing platform for the early diagnosis of PD and can be applied to detect other protein biomarkers, such as PD-L1.

Immobilization for Lipase: Enhanced Activity and Stability by Flexible Combination and Solid Support.

In this study, an enhanced activity and stability method for immobilizing porcine pancreatic lipase (PPL) was developed based on ZIF-8 encapsulated supramolecular-modified gold nanoparticle complexes (pSC4-AuNPs@ZIF-8). Supramolecular calix[4]arene (pSC4) can recognize the amino group of PPL through non-covalent force, and this flexible binding method protected the structure of PPL during the immobilization process. Due to the hydrophilic of pSC4-AuNPs and hydrophobic of ZIF-8, PPL can maintain a "lid open" conformation, which can enhance the stability of PPL structure and reduce PPL activity loss. ZIF-8 was used to immobilize PPL to avoid the difficult recovery of free PPL. Compared with the native form of PPL, it exhibited 70.6% maintained activity with terrific pH and temperature stability, and had good performance in thermal stability, time stability, and reusability. In addition, three immobilized PPL methods were designed to further clarify the influence of synthetic methods and additives on the activity and stability of PPL. Importantly, the loading rate of pSC4-AuNPs@ZIF-8@PPL was up to 51.2% among these immobilized PPL systems. Therefore, pSC4-AuNPs@ZIF-8 may serve as a versatile and promising immobilization system for enzymes.