Application of Quantum Dots in Lateral Flow Immunoassays: Non-Communicable and Communicable Diseases

Quantum Dots (QDs) are ideal fluorescent labels for lateral flow assays (LFA) due to their unique optical properties and resistance to chemical and photo-degradation. Lateral flow assay, known as immunochromatography test, is a diagnostic strip test that uses paper or membrane-based devices to detect the presence/absence of an analyte with the pregnancy test, the most known LFA. Diagnostic tools for non-communicable (NCDs) and communicable diseases (CDs) are available. However, other NCDs and CDs do not have LFAs as first-line diagnosis/point-of-care. QDs are promising fluorescent labels as they improve the LFA’s colourimetric sensitivity and fluorescence stability. This chapter discusses the tailoring and application of QDs in LFA. Particular focus on the applications of QDs in LFA for detecting or screening NCDs (i.e. cancers etc.) and CDs (i.e. SARS-CoV-2, HIV/AIDs etc.).The book chapter concludes by discussing different challenges and perspectives of QDs in LFA

Mn-Doped ZnSe Quantum Dots as Fluorimetric Mercury Sensor

Quantum dots (QDs), because of their exciting optical properties, have been explored as alternative fluorescent sensors to conventional organic fluorophores which are routinely employed for the detection of various analytes via fluorometry. QD probes can detect toxic metal ions, anions, organic molecules with good selectivity and sensitivity. This chapter investigates the synthesis of Mn-doped ZnSe QDs using nucleation-doping strategy. The as-synthesized QDs were characterized by various analytical tools such as ultraviolet-visible (UV-vis) absorption, photoluminescence (PL) spectroscopy, X-ray diffractometry (XRD) and transmission electron microscopy (TEM). It was found that Mn doping of QDs significantly increases the PL intensity. The PL of the resulting QDs was examined in the presence of different metal ions to check its selective response. Among the various metal ions, Hg2+ exhibits a drastic quenching of the QD’s emission intensity. A Stern-Volmer plot of [Hg2+] sensing using the as-synthesized QDs showed linearity in the range of 0–30 × 10−6 ML−1 with the regression coefficient R2 = 0.99. The detection limit was found to be 6.63 × 10−7 ML−1. Thus, the present Mn-doped ZnSe QDs represent a simple, non-toxic fluorescent probe for the qualitative and quantitative detection of mercury ions in aqueous samples

One-pot synthesis optimization of thiol-capped SnS and SnS/ZnS QDs for photocatalytic degradation of Rhodamine 6G

Interest in SnS-based quantum dots (QDs) has increased due to their low toxicity, widespread natural availability, and superior electro-optical characteristics suitable for photodegradation applications. Herein, we report the synthesis of SnS-based QDs using thiourea and tin (II)chloride as salt precursors. The study explored the impact of various synthetic parameters such as pH, capping ligand, Sn:S ratio, reaction solvent, and ZnS shell on the optical characteristics of the synthesized QDs. The optimal QDs properties were observed at pH = 3 and Sn:S ratio = 1:1. Transmission electron microscopy analysis showed spherical nanoparticles, while the Fourier Transform Infrared spectroscopy revealed QDs with thiol capping. Time-dependent studies revealed that when the QDs were synthesized using propylene glycol, the ultraviolet-visibile (UV–vis) spectrum exhibited an increase in absorbance over time and improved stability compared to aqueous synthesized QDs. SnS/ZnS QDs capped with 3-mercaptopropanoic acid exhibited improved photoluminscence (PL) emissions, stability, and aqueous dispersion compared to glutathione and l-Cysteine as thiol-capping agents. The photocatalytic activity of SnS/ZnS QDs was assessed against Rhodamine 6G and increased to 65 % when passivated with ZnS compared to 31 % for the core SnS QDs. With the given findings, this study supports the stability and effectiveness of the SnS/ZnS QDs as a viable dye degradant

Porphyrin as Diagnostic and Therapeutic Agent

The synthesis and application of porphyrins has seen a huge shift towards research in porphyrin bio-molecular based systems in the past decade. The preferential localization of porphyrins in tumors, as well as their ability to generate reactive singlet oxygen and low dark toxicities has resulted in their use in therapeutic applications such as photodynamic therapy. However, their inherent lack of bio-distribution due to water insolubility has shifted research into porphyrin-nanomaterial conjugated systems to address this challenge. This has broadened their bio-applications, viz. bio-sensors, fluorescence tracking, in vivo magnetic resonance imaging (MRI), and positron emission tomography (PET)/CT imaging to photo-immuno-therapy just to highlight a few. This paper reviews the unique theranostic role of porphyrins in disease diagnosis and therapy. The review highlights porphyrin conjugated systems and their applications. The review ends by bringing current challenges and future perspectives of porphyrin based conjugated systems and their respective applications into light

The Therapeutic Effect of Second Near-Infrared Absorbing Gold Nanorods on Metastatic Lymph Nodes via Lymphatic Delivery System

Photothermal therapy has been established recently as a non-invasive treatment protocol for cancer metastatic lymph nodes. Although this treatment approach shows efficient tumour ablation towards lymph node metastasis, the monitoring and reporting of treatment progress using the lymphatic delivery channel still need to be explored. Herein, we investigated the anti-tumour effect of pegylated gold nanorods with a high aspect ratio (PAuNRs) delivered via the lymphatic route in a mouse model. In this study, breast carcinoma (FM3A-Luc) cells were inoculated in the subiliac lymph node (SiLN) to induce metastasis in the proper axillary lymph node (PALN). The treatment was initiated by injecting the PAuNRs into the accessory axillary lymph node (AALN) after tumour metastasis was confirmed in the PALN followed by external NIR laser irradiation under a temperature-controlled cooling system. The anti-tumour impact of the treatment was evaluated using an in vivo bioluminescence imaging system (IVIS). The results showed a time-dependent reduction in tumour activity with significant treatment response. Tumour growth was inhibited in all mice treated with PAuNRs under laser irradiation; results were statistically significant (** p < 0.01) even after treatment was concluded on day 3. We believe that this non-invasive technique would provide more information on the dynamics of tumour therapy using the lymphatically administered route in preclinical studies