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L‐3,4‐dihydroxyphenylalanine (levodopa or L–DOPA) a precursor of neurotransmitter dopamine, has been universally prescribed as a gold standard for treatment of Parkinson's Disease (PD). However, direct administration of L–DOPA has risky adverse effects which makes it challenging in the treatment of PD. Hence developing simple detection platform for sensing of L–DOPA is significant. In this work, we have developed cysteine stabilized copper nanocluster quenched with Fe2+ (Fe2+@cys@CuNC) and used as both fluorescent and colorimetric probe for detection of L–DOPA. L–DOPA attributed a fluorescence quenching effect on developed probe. Fe2+@cys@CuNC detected L–DOPA within a linear range from 0.06 mM to 1.31 mM with a low limit of detection (LoD) of 6.57 nM. The probe also exhibited high selectivity for L–DOPA over other biomolecules and neurotransmitters. Furthermore, the capability of this probe was validated by sensing L–DOPA from human serum with excellent recovery rates of 85.75 % to 115.07 %. A low‐cost paper strip‐based portable detection platform was also developed for visual detection of L–DOPA. [ABSTRACT FROM AUTHOR]

Cardiac troponin I (cTnI) is a significant biomarker for acute heart attack. Hence, fast, economical, easy and real time monitoring of cardiac troponin I (cTnI) is of great importance in diagnosis and prognosis of heart failure in the healthcare domain. In this work, an immunoassay based on NaYF4:Yb/Ho based photon-upconversion nanoparticle (UCNP) with narrow emission peaks at 540 nm and 655 nm respectively, is synthesized. Then, it is encapsulated with amino functionalized silica using 3-aminopropyltriethoxysilane (APTES) to form APTES@SiO2-NaYF4:Yb/Ho UCNPs. When AuNPs is added to this system, the fluorescence is quenched by the electrostatic interaction with APTES@SiO2-NaYF4:Yb/Ho UCNPs, thereby exhibiting a FRET-based biosensor. When the cTnI antigen is introduced into the developed probe, an antibody–antigen complex is formed on the surface of the UCNPs resulting in fluorescence recovery. The developed sensor shows a linear response towards cTnI in the range from 0.1693 ng mL−1 to 1.9 ng mL−1 with a low limit of detection (LOD) of 5.5 × 10−2 ng mL−1. The probe exhibits adequate selectivity and sensitivity when compared with coexisting cardiac biomarkers, biomolecules and in real human serum samples. [ABSTRACT FROM AUTHOR]

There is a significant drive to identify a unified emission mechanism hidden behind carbon nanodots (CDs) to attain reliable control over their photoluminescence properties. This issue is addressed here by investigating the fluorescence response of citric acid and urea-based nitrogen doped carbon nanodots (NCDs) towards transition metal ions in solutions of different polarities/viscosities/hydrogen bonding strengths. The photoluminescence from NCDs upon excitation at 400 nm is quenched by metal ions such as chromium(VI), ruthenium(III) and iron(III) in two different polar solvents, protic water and aprotic dimethylsulphoxide (DMSO). This amplified luminescence quenching in polar solutions showed significant static quenching contributions. The quenching phenomenon highly depends on the excitation wavelength and solvent environment. The fluorescence quenching sequence reveals that pyridinic nitrogen-bases have a dominant influence on J-like emissive aggregates of NCDs. Similarly, oxygen-containing functional groups play a significant role in constructing H-aggregates of NCDs. The most intense emission is contributed by the J-like assembly of H-aggregates. [ABSTRACT FROM AUTHOR]

Cardiac troponin I (cTnI) is a significant biomarker for acute heart attack. Hence, fast, economical, easy and real time monitoring of cardiac troponin I (cTnI) is of great importance in diagnosis and prognosis of heart failure in the healthcare domain. In this work, an immunoassay based on NaYF 4 :Yb/Ho based photon-upconversion nanoparticle (UCNP) with narrow emission peaks at 540 nm and 655 nm respectively, is synthesized. Then, it is encapsulated with amino functionalized silica using 3-aminopropyltriethoxysilane (APTES) to form APTES@SiO 2 -NaYF 4 :Yb/Ho UCNPs. When AuNPs is added to this system, the fluorescence is quenched by the electrostatic interaction with APTES@SiO 2 -NaYF 4 :Yb/Ho UCNPs, thereby exhibiting a FRET-based biosensor. When the cTnI antigen is introduced into the developed probe, an antibody-antigen complex is formed on the surface of the UCNPs resulting in fluorescence recovery. The developed sensor shows a linear response towards cTnI in the range from 0.1693 ng mL -1 to 1.9 ng mL -1 with a low limit of detection (LOD) of 5.5 × 10 -2 ng mL -1 . The probe exhibits adequate selectivity and sensitivity when compared with coexisting cardiac biomarkers, biomolecules and in real human serum samples.