Search

Ncediwe Tsolekile,1– 3 Sundararajan Parani,2,3 Erenilda Ferreira de Macedo,4 Thabang Calvin Lebepe,2,3 Rodney Maluleke,2,3 Vuyelwa Ncapayi,2,3 Mangaka Clara Matoetoe,1 Sandile Phinda Songca,5 Katia Conceição,6 Dayane Batista Tada,4 Oluwatobi Samuel Oluwafemi2,3 1Department of Chemistry, Cape Peninsula University of Technology, Cape Town, 2000, South Africa; 2Department of Chemical Sciences, University of Johannesburg, Johannesburg, 2028, South Africa; 3Centre for Nanomaterials Science Research, University of Johannesburg, Johannesburg, South Africa; 4Laboratory of Nanomaterials and Nanotoxicology, Institute of Science and Technology, Federal University of São Paulo, São Paulo, Brazil; 5Department of Chemistry, University of KwaZulu-Natal, Durban, 4000, South Africa; 6Laboratory of Peptide Biochemistry, Institute of Science and Technology, Federal University of São Paulo, São Paulo, BrazilCorrespondence: Oluwatobi Samuel Oluwafemi, Department of Chemical Sciences, University of Johannesburg, P. O. Box 17011, Doornfontein, Johannesburg, 2028, South Africa, Tel +27 011 559 9060, Email oluwafemi.oluwatobi@gmail.com Dayane Batista Tada, Laboratório de Nanomateriais e Nanotoxicologia, Universidade Federal de São Paulo, Talim, 330 - Vila Nair, São José dos Campos, São Paulo, 12231-280, Brazil, Email day.tada@gmail.comBackground: Photodynamic therapy (PDT) is a non-invasive treatment modality that destroys abnormally growing cells or microorganisms. Porphyrins are used as photosensitizers in PDT; however, their clinical application has been limited by their poor water solubility, resulting in aggregation and low quantum yields of reactive oxygen species (ROS).Methods: To overcome these limitations and improve PDT efficacy, we herein report the conjugation of ZnCuInS/ZnS (ZCIS/ZnS) quantum dots (QDs) to 5,10,15,20-tetrakis(3-hydroxyphenyl)porphyrin (mTHPP). The optimal conditions for QDs porphyrin conjugation formation were systematically evaluated.Discussion: This study further assessed the PDT efficacy and antibacterial potency of the synthesized ZCIS/ZnS-mTHPP conjugates. The PDT efficacy of the QDs, mTHPP, and conjugate was evaluated against the murine metastatic melanoma (B16 F10 Nex2) cell line. This was performed with and without LED irradiation.Results: The conjugate exhibited the highest reduction in cell viability following LED irradiation (72%) compared to the bare QDs (19%) and mTHPP (1%). Antimicrobial studies conducted on E. coli showed that the conjugation exhibits a higher antibacterial effect than the bare QDs, even without light.Conclusion: The results suggest that conjugate is a promising class of materials for anti-cancer and antimicrobial PDT.Keywords: Zn-Cu-In-S/ZnS QDs, 5,10,15,20-tetrakis(hydroxyphenyl)porphyrin, mTHPP, photodynamic therapy, murine metastatic melanoma (B16F10-Nex2), antibacterial activity

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.

The toxicity of heavy metals present in binary semiconductor nanoparticles also known as quantum dots (QDs) has hindered their wide applications hence the advent of non-toxic ternary quantum dots. These new group of quantum dots have been shown to possess some therapeutic action against cancer cell lines but not significant enough to be referred to as an ideal therapeutic agent. In this report, we address this problem by conjugating red emitting CuInS/ZnS QDs to a 5,10,15,20-tetrakis(3-hydroxyphenyl)porphyrin -photosensitizer for improved bioactivities. The glutathione capped CuInS/ZnS QDs were synthesized in an aqueous medium using a kitchen pressure cooker at different Cu: In ratios (1:4 and 1:8) and at varied temperatures (95 °C, 190 °C and 235 °C). Optical properties show that the as-synthesized CuInS/ZnS QDs become red-shifted compared to the core (CuInS) after passivation with emission in the red region while the cytotoxicity study revealed excellent cell viability against normal kidney fibroblasts (BHK21). The highly fluorescent, water-soluble QDs were conjugated to 5,10,15,20-tetrakis(3-hydroxyphenyl)porphyrin (mTHPP) via esterification reactions at room temperature. The resultant water-soluble conjugate was then used for the cytotoxicity, fluorescent imaging and gene expression study against human monocytic leukemia cells (THP-1). Our result showed that the conjugate possessed high cytotoxicity against THP-1 cells with enhanced localized cell uptake compared to the bare QDs. In addition, the gene expression study revealed that the conjugate induced inflammation compared to the QDs as NFKB gene was over-expressed upon cell inflammation while the singlet oxygen (1O2) study showed the conjugate possessed large amount of 1O2, three times than the bare porphyrin. Thus, the as-synthesized conjugate looks promising as a therapeutic agent for cancer therapy.

The inherent heavy metal toxicity of fluorescent binary quantum dots (QDs) despite their excellent optical properties has limited their biological applications. This has shifted the research focus towards toxic-metal free chalcopyrite ternary QDs such as AgInS2 (AIS), CuInS2 (CIS), ZnInS (ZIS) QDs etc. Among these QDs, ZIS has been given less attention irrespective of its advantages over other conventional ternary QDs. This is attributed to the difficulty in producing zero dimensional (0D) ZIS via an aqueous synthetic route compared to other morphologies. We herein report the facile and ecofriendly aqueous synthesis, properties and cellular activity of 0D ZIS. The synthesis was carried out via a reflux method using thioglycolic acid (TGA) and gelatin as a capping ligand and a stabilizer. The temporal evolution of the optical properties was investigated by varying the pH, TGA concentration, amount of gelatin, Zn/In ratio and sulfur concentration. The as-synthesized QDs show narrow emission, with pH, TGA concentration and sulfur concentration showing a great influence on the emission intensity. The optimized parameters for better fluorescence was obtained at pH = 7, 21.5 mmol of TGA and Zn : In ratio = 1 : 4. Transmission electron microscopy (TEM) images showed that the as-synthesised ZIS QDs are small, monodispersed, crystalline and spherical in shape with an average particle size of 3 nm while Fourier transform infrared (FTIR) spectra confirmed the capping of ZIS QDs by TGA and gelatin. The as-synthesized QDs are highly stable with excellent biocompatibility towards normal cells (BHK-21) and cancerous cells (HeLa) even at high concentration (1000 μg mL−1).

Background Metal-free, water-soluble and highly stable meso-tetra-(4-sulfonatophenyl) porphyrin (TPPS4) has been studied for their singlet oxygen quantum yield. However, TPPS4 suffers from inherent shortcomings. To address these, TPPS4 was conjugated to ternary copper indium sulphide/ zinc sulphide (CuInS2/ZnS) quantum dots (QDs). Purpose We herein report for the first time the synthesis of TPPS4-CuInS/ZnS QDs conjugate as an improved photosensitizer. Methods Water-soluble TPPS4 was synthesized from tetraphenylporphyrin (TPPH2) after silica-gel purification. The CuInS/ZnS QDs were synthesized by hydrothermal method at a Cu:In ratio of 1:4. The porphyrin-QDs conjugate was formed via the daggling sulfonyl bond of the porphyrin and amine bond of the QDs. The effect of pH on the optical properties of TPPS4 was evaluated. The effect of Zn:Cu + In ratio on the ZnS shell passivation was examined to reduce structural defects on the as-synthesized QDs. Results Various spectroscopic techniques were used to confirm the successful conversion of the organic TPPH2 to water-soluble TPPS4. The singlet oxygen generation evaluation shows an improved singlet oxygen quantum yield from 0.19 for the porphyrin (TPPS4) alone to 0.69 after conjugation (CuInS/ZnS-TPPS4) with an increase in the reaction rate constant (k (s-1)).

We herein report a facile synthesis of AgInSe2 nanorods with a high aspect ratio in the aqueous phase via a completely green method without the use of any surfactant or template. It was found that the amount of selenium precursor concentration has greater control over the morphology of the nanocrystals. The higher concentration of selenium (Ag:In:Se = 1:4:6.2) in the reaction produced long nanorods with a high aspect ratio (> 30) together with few spherical nanocrystals, whereas the lower Se concentration of selenium (Ag:In: Se = 1:4:3.75 or 3.85) produced aggregates of spherical particles with particle diameter of 5.2 ± 0.4 nm. We inferred that increase in the reaction kinetic drive coupled with slower growth rate as the selenium concentration increased enhanced more interaction between the existing spherical particles in the product solution and resulted in the formation of elongated particles. This method is simple, cost-effective and eco-friendly for the synthesis of Se based ternary semiconductor nanorods.

Hexadecylamine (HDA) capped CdSe/ZnSe core/shell and ZnxCd1−xSe alloy quantum dots (QDs) have been synthesized successfully via a non-organometallic, hot injection method. The optical, structural and morphological properties of the as-synthesized QDs were determined by using, UV–visible (UV–Vis) and photoluminescence spectroscopy, X-ray diffraction and transmission electron microscopy (TEM). The effect of reaction time and temperature on the core/shell and alloy formation were investigated in detail. The addition of ZnSe precursor to the pre-synthesized HDA capped CdSe QDs at 230 °C produced core/shell CdSe/ZnSe QDs whereas at 250 °C an alloy QDs were obtained initially which later transformed to core/shell structure with time. On the other hand, the immediate addition of ZnSe precursor to the hot CdSe-precursor solution in HDA at 230 °C resulted in HDA capped ZnxCd1−xSe alloy QDs. The optical and structural characterisation shows that the as-synthesised core–shell and alloy QDs are of high quality. This method is simple, and fast for the preparation of core/shell and alloy binary QDs and will encourage their synthesis for various industrial applications.

Quantum dots (QDs) have been resourceful in bio-applications such as fluorescent tagging, sensing, and bio-assays. Their bio-recognition and subsequent acceptance as foreign bodies by biomolecules largely depend on the surface structure of the QDs. Surface functionalization is thus a critical factor in their synthesis and design. In this work, we report on the surface modification of CuInS/ZnS QDs by an α-amino acid which plays an essential role in cell division and wound healing. The CuInS/ZnS QDs was synthesized via one-step eco-friendly method in a pressure cooker. To improve the biocompatibility and stability, the purified QDs were functionalized with l -arginine using carbodiimide chemistry to produce arginine (Arg) functionalized CuInS/ZnS QDs. Interest in the use of l -arginine amino acid in this study is a result of its zwitterion state, physiological properties, and most importantly its backbone structure which enables ease of conjugation. The Arg-CuInS/ZnS QDs were then conjugated to 5, 10, 15, 20-meso (hydroxyphenyl) porphyrin (mTHPP), a second-generation photosensitizing drug to improve the absorption efficiency of the porphyrin and tagging of cancer cells. This study examined for the first time the effect of amino acid functionalization on the luminescent, absorption and morphology properties of ternary CuInS/ZnS QDs and its porphyrin conjugate using various optical analyses. Furthermore, this study investigated the bio-labeling properties of the prepared material and tested this against leukemia (THP-1) cancer cell lines. The as-synthesized water-soluble biocompatible Arg-CuInS/ZnS - mTHPP conjugate proved to be useful for surface functionalization and as a possible bio-labeling agent.

Porphyrins are photosensitisers used in photodynamic therapy (PDT) due to their tumor localization and in situ singlet oxygen generation. However, their limited absorption, insolubility, and aggregation in an aqueous medium limited their effective application in PDT. To overcome these limitations, we herein, report a large-scale aqueous synthesis of CulnS2/ZnS ternary quantum dots, and its conjugation to 5,10,15, 20-meso(4-hydroxyphenyl) porphyrin. The singlet oxygen generation of this highly aqueous soluble novel conjugate shows its potential for PDT applications.

Specially designed functionalized nanomaterials such as superparamagnetic iron oxide, gold, quantum dots and up- and down-conversion lanthanide series nanoparticles have consistently and completely revolutionized the biomedical environment over the past few years due to their specially inferring properties, such as specific drug delivery, plasmonic effect, optical and imaging properties, therapeutic thermal energy productionand excellent irresistible cellular penetration. These properties have been used to improve many existing disease treatment modalities and have led to the development of better therapeutic approaches for the advancement of the treatment of critical human diseases, such as cancers and related malaise. In photodynamic therapy, for example, where the delivery of therapeutic agents should ideally avoid toxicity on nearby healthy cells, superparamagnetic iron oxide nanoparticles have been shown to be capable of making photodynamic therapy (PDT) prodrugs and their associative targeting moieties tumor-specific via their unique response to an external magnetic fields. In this review, the nanomaterials commonly employed for the enhancement of photodynamic therapy are discussed. The review further describes the various methods of synthesis and characterization of these nanomaterials and highlights challenges for improving the efficacy of PDT in the future.

The link between the microbiome and cancer has led researchers to search for a potential probe for intracellular targeting of bacteria and cancer. Herein, we developed near infrared-emitting ternary AgInSe/ZnS quantum dots (QDs) for dual bacterial and cancer imaging. Briefly, water-soluble AgInSe/ZnS QDs were synthesized in a commercial kitchen pressure cooker. The as-synthesized QDs exhibited a spherical shape with a particle diameter of 4.5 ± 0.5 nm, and they were brightly fluorescent with a photoluminescence maximum at 705 nm. The QDs showed low toxicity against mouse mammary carcinoma (FM3A-Luc), mouse colon carcinoma (C26), malignant fibrous histiocytoma-like (KM-Luc/GFP) and prostate cancer cells, a greater number of accumulations in Staphylococcus aureus, and good cellular uptake in prostate cancer cells. This work is an excellent step towards using ternary QDs for diagnostic and guided therapy for prostate cancer.

Conjugation of photosensitizers (PS) with nanoparticles has been largely used as a strategy to stabilize PS in the biological medium resulting in photosensitizing nanoparticles of enhanced photoactivity. Herein, (Meso-5, 10, 15, 20-tetrakis (3-hydroxyphenyl) phorphyryn (mTHPP) was conjugated with diamond nanoparticles (ND) by covalent bond. Nanoconjugate ND-mTHPP showed suitable stability in aqueous suspension with 58 nm of hydrodynamic diameter and Zeta potential of −23 mV. The antibacterial activity of ND-mTHPP was evaluated against Escherichia coli for different incubation times (0–24 h). The optimal activity was observed after 2 h of incubation and irradiation (660 nm, 51 J/cm2) performed right after the addition of ND-mTHPP (100 μg/mL) to the bacterial suspension. The inhibitory activity was 56% whereas ampicillin at the same conditions provided only 14% of bacterial growth inhibition. SEM images showed agglomerate of ND-mTHPP adsorbed on the bacterial cell wall, suggesting that the antimicrobial activity of ND-mTHPP was afforded by inducing membrane damage. Cytotoxicity against murine embryonic fibroblast cells (MEF) was also evaluated and ND-mTHPP was shown to be noncytotoxic since viability of cells cultured for 24 h in the presence of the nanoconjugate (100 μg/mL) was 78%. Considering the enhanced antibacterial activity and the absence of cytotoxic effect, it is possible to consider the ND-mTHPP nanoconjugate as promising platform for application in antimicrobial photodynamic therapy (aPDT).

The paradigm-shift in quantum dot (QDs) synthesis and applications in the past decade have seen the development of an array of semiconductor QDs. The II–VI or IV–VI QDs are still the most researched QDs undoubtedly. However, safer alternatives within the ternary I–III–VI QDs are currently being pursued. This has resulted in an increased new body of knowledge on nanomaterial technology. This paper reviews the evolution of synthetic methods for I–III–VI QDs and their surface modification techniques with a particular focus on the ternary copper-indium-sulphide (CIS) based QDs. The parameters that play a vital role in the optical properties of CIS QDs, and their various applications with emphasis on biological applications are also discussed. The review ends with the challenge and future perspective of these nascent QDs.

A new hydrothermal method for the synthesis of thiol-protected CdSe/CdS core/shell quantum dots (QDs) starting from thiolated cadmium and selenium is reported. Four different thiols namely; 3-mercaptopropane-1-sulfonic acid (MPSA), 2-mercaptosuccinic acid, 3-mercaptopropanoic acid (MPA) and 2-mercaptoacetic acid were used to prepare the precursors which also served as capping agent and sulphur source. The as-synthesized QDs were characterized by ultraviolet–visible (UV–Vis) and photoluminescence (PL) spectroscopy, fourier transform infrared spectroscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy, Raman spectroscopy and transmission electron microscopy. The as-prepared QDs exhibited broad trap emission with longer lifetime (>100 ns) due to thiolate trap sites. The particle growth kinetics and the photoluminescent quantum yield (PLQY) of the resulting QDs were found to be depended on the type of thiol and pH. The MPA capped QDs synthesized at pH 11.0 exhibited the high PLQY among other thiol capped QDs. The size of the QDs was calculated to be ~3 nm by XRD analysis, which is consistent with TEM results. The possible mechanism of the core/shell formation is also presented.

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.

I-III-VI chalcopyrite ternary quantum dots have emerged as a good alternative over the conventional II-VI and IV-VI chalcogenide binary QDs that usually consist of heavy metals such as Cd and Pb which has limited their bioapplications. Among the chalcopyrite QDs, AgInSe

Ternary I-III-VI quantum dots (QDs) have become attractive fluorescent materials due to their low toxicity compared to conventional binary II-VI based QDs. However, these QDs have been majorly synthesized in an organic medium under harsh conditions which is not eco-friendly. Herein, we report aqueous synthesis of glutathione (GSH) capped Cu–In–S based QDs using reflux approach at 95 °C and investigated the effect of synthetic parameters such as Cu:In precursor ratio, pH and the amount of GSH on the core QDs.. The as-synthesized material was characterized using Ultraviolet–Visible (UV–vis) absorption, Photoluminescence (PL), Fourier Transform Infrared spectroscopy (FT-IR), X-ray diffraction (XRD) and transmission electron microscopy (TEM) techniques. Passivation of the core QDs with ZnS increased its photoluminescence with a blue shifted absorption and emission wavelength. Structural investigation of the QDs by using TEM, XRD and EDS techniques indicated the possible formation of Cu–In–Zn–S/ZnS “alloy-core/shell” structure due to the diffusion of Zn from ZnS shell into Cu–In–S crystal lattice and its occupation at vacant sites.

I-III-VI chalcopyrite ternary quantum dots have emerged as a good alternative over the conventional II-VI and IV-VI chalcogenide binary QDs that usually consist of heavy metals such as Cd and Pb which has limited their bioapplications. Among the chalcopyrite QDs, AgInSe2 QDs has been the least developed due to the imbalanced cation reactivity, unwanted impurities, broad size distribution and resultant large particle sizes. In addition, the cell viability of these QDs still needs to be investigated on different cell lines both normal and cancerous ones. Herein, large-scale synthesis of water-soluble thioglycolic acid (TGA) capped and gelatin-stabilized AgInSe2 (AISe) core and AgInSe2/ZnSe (AISe/ZnSe) core/shell QDs in the absence of an inert atmosphere and their cell viability against different cell lines are reported. The optical and structural characteristics of the as-synthesized QDs were investigated by UV–visible (vis) absorption, photoluminescence (PL) and Fourier-transmission infrared (FTIR) spectroscopies, dynamic light scattering (DLS), X-ray diffraction (XRD), and high-resolution transmission electron microscope (HRTEM) techniques. Growth of ZnSe shell on the core AISe resulted in the blue shifting of the emission maximum position with the increased PL intensity. The QDs are small and spherical in shape with an average particle diameter of 2.8 nm and 3.2 nm for AISe and AISe/ZnSe QDs respectively. The in vitro cell viability assay revealed that the as-synthesized AISe/ZnSe QDs are not toxic towards cancerous (HeLa -cervical cancer and A549-lung cancer) and normal (BHK21 –Kidney) cell lines.