Au-Fe_(3)O_(4) dumbbell-like nanoparticles based lateral flow immunoassay for colorimetric and photothermal dual-mode detection of SARS-CoV-2 spike protein

Lateral flow immunoassay(LFIA)has become popular in laboratories,at-home testing,and medical diagnostics due to its minimal cost and user-friendliness.Nevertheless,conventional test strips based on colloidal gold can only obtain qualitative or semi-quantitative results with low sensitivity.In this work,AuFe_(3)O_(4) dumbbell-like nanoparticles were synthesized and used as the LFIA labelling marker for highly sensitive colorimetric-photothermal dual-mode detection of SARS-CoV-2 spike(S)protein.The unique dumbbell structure of Au-Fe_(3)O_(4) NPs makes it possible to combine the best features of both Au NPs and Fe_(3)O_(4) NPs.The increased surface area of these NPs enhances their LSPR effect and photothermal effect,which achieves signal amplification to increase sensitivity.The Au-Fe_(3)O_(4) NPs modified with S protein antibody could identify S protein in samples,which were recognized and accumulated on T-line by another antibody,generating color band for qualitative colorimetric detection.The T-line was irradiated by laser to obtain temperature change for quantitative detection of photothermal.In optimized conditions,the detection limit was 1.22 pg/m L,three orders of magnitude more sensitive than colorimetric detection.Finally,the approach was performed on SARS-CoV-2 pseudovirus samples and outperformed traditional colloidal gold strips.This LFIA platform exhibits significant promise for practical implementation,as it can satisfy the need for low-cost,high-sensitivity,and home-based quantitative detection for respiratory infectious diseases.

Synthesis and Structure Investigation of a Transition Metal Ion Bridging Bis(diphosphopentamolybdates),[H_2BIIM]_3[HBIIM]_4[Mn(H_2O)_4(P_2Mo_5O_(23))_2]·7H_2O

A novel transition metal ion bridging bis（diphosphopentamolybdates） has been synthesized and characterized by elemental analysis,IR spectrum,UV spectrum and single-crystal X-ray diffraction.The single-crystal structure analysis shows that the compound consists of seven charge-compensating 2,2＇-biimidazole cations （BIIM=2,2＇-biimidazole） and one dumbbell-like [Mn（H2O）4（P2Mo5O23）2]10-heteropolyanion which is constructed by two [P2Mo5O23]6-clusters bridged through one [Mn（H2O）4]2＋ cation.

CXCR4 Peptide Conjugated Au-Fe2O3 Nanoparticles for Tumor-targeting Magnetic Resonance Imaging

Peptide-functionalized Au-Fe2O3 nanoparticles（termed as anti-CXCR4-Au-Fe2O3 NPs） have been constructed through conjugation of dumbbell-like Au-Fe203 NPs with C-X-C motif chemokine receptor 4（CXCR4） binding cyclic peptide. One dumbbelMike Au-Fe2O3NP composes an Au NP[（3.3±0.3） nm in diameter] for conjugating CXCR4 binding cyclic peptide through Au-S covalent bond and a Fe2O3 NP[（8.7±0.8） nm in diameter] for using as T2-weighted magnetic resonance imaging（MRI） contrast agent. The anti-CXCR4-Au-Fe2O3 NPs have reasonable biocompatibility and integration of T2-weighted MRI contrast and tumor-targeting functionalities. The anti- CXCR4-Au-Fe2O3 NPs exhibit strong interactions with two kinds of breast tumor cells, MCF-7 cells and MDA-MB-231 cells, and high negative contrast in MRI of MDA-MB-231 tumor bearing mouse with 62% decreasing of MRI signal, indicating that the anti-CXCR4-Au-Fe2O3 NPs can recognize tumor with high efficacy and specificity.