Review Article PHARMACEUTICAL AND BIOPHARMACEUTICAL ASPECTS OF QUANTUM DOTS-AN OVERVIEW SADDAM C. SHAIKH 1 , SHWETA G. SABOO 2 , PRASHANT S. TANDALE 3 , FAHIM S. MEMON 4 , SHARAD D. TAYADE 4* , M. AKIFUL HAQUE 5 , SHARUK L. KHAN 6 1 Department of Pharmaceutics (D Pharm), Rajarshi Shahu College of Pharmacy, Buldana, Maharashtra, India 443001, 2 Department of Pharmacognosy, Government College of Pharmacy, Karad, Maharashtra, India 415124, 3 Department of Pharmaceutics, School of Pharmaceutical Sciences, Lovely Professional University, Punjab, India 144001, 4 Department of Pharmaceutics, Rajarshi Shahu College of Pharmacy, Buldana, Maharashtra, India-443001, 5 Department of Pharmaceutical Analysis, Anurag University, Venkatapur, Hyderabad, India 500088, 6 Department of Pharmaceutical Chemistry, MUP's College of Pharmacy (B Pharm), Degaon, Risod, Washim, Maharashtra, India 444504 Emails: sharad_tayade1@rediffmail.com Received: 23 Mar 2021, Revised and Accepted: 12 May 2021 ABSTRACT In the twenty-first century, nanotechnology has become cutting-edge technology. It is interdisciplinary and multidisciplinary, covering numerous fields such as medicine, engineering, biology, physics, material sciences, and chemistry. The present work aims to cover the optical properties, method of preparations, surface modifications, bio-conjugation, characterization, stability, and cytotoxicity of quantum dots (QDs). Articles were reviewed in English literature reporting the pharmaceutical and bio-pharmaceutical aspects of QDs which were indexed in Scopus, web of science, google scholar and PubMed without applying the year of publication criterion. One significant value of utilizing nanotechnology is that one can alter and control the properties in a genuinely unsurprising way to address explicit applications' issues. In science and biomedicine, the usage of functional nanomaterials has been broadly investigated and has become one of the quick-moving and stimulating research directions. Different types of nanomaterial (silicon nanowires, QDs, carbon nanotubes, nanoparticles of gold/silver) were extensively utilized for biological purposes. Nanomedicine shows numerous advantages in the natural characteristics of targeted drug delivery and therapeutics. For instance, protection of drugs against degradation, improvement in the drug's stability, prolonged circulation time, deceased side effects, and enhanced distribution in tissues. The present review article deals with the quantum dots, their optical properties, method of preparations, surface modifications, bio-conjugation, characterization, stability, and cytotoxicity of quantum dots. The review also discusses various biomedical applications of QDs. The QDs-based bio-nanotechnology will always be in the growing list of unique applications, with progress being made in specialized nanoparticle development, the detection of elegant conjugation methods, and the discovery of new targeting ligands. Keywords: Quantum dots, Optical properties, Microwave-assisted method, Cytotoxicity, Cell imaging, Sentinel lymph-node mapping © 2021 The Authors. Published by Innovare Academic Sciences Pvt Ltd. This is an open access article under the CC BY license (https://creativecommons.org/licenses/by/4.0/) DOI: https://dx.doi.org/10.22159/ijap.2021v13i4.41623. Journal homepage: https://innovareacademics.in/journals/index.php/ijap INTRODUCTION In 1981, Ekimov and Onushenko described the Quantum dots (QDs), also called nanoscale semiconductor crystals [1]. The quantum dots are made up of material from periodic table group II-VI (CdSe) or III- V (InP) [2–6]. The most well studied and broadly utilized QDs are the cadmium selenide (Cd/Se) [3]. The cores and QDs targeting are protected by surface modification, and such changes significantly improve QDs sizes [7]. There are two kinds of fluorescent-based quantum dots, namely graphene and carbon quantum dots [8]. Quantum dots possess quantum confinement property and, on excitation from visible to infra-red wavelength, emit fluorescence [9, 10]. Usually, in the crystal core of a single QD, around 100-100,000 atoms are present. The size of QDs usually lies in between 2-10 nm diameter, which generally grows up to 5-20 nm in diameter after encapsulation of polymer [11, 12]. QDs comprise a semiconductor core, which is over-covered by shell and cap. The anatomy of QDs is represented in fig. 1 [13]. Semiconducting character and optical properties depend on the inorganic core. In QDs synthesis, the organic surfactants are developed and eventually shape ligands on the core surface [14–17]. The nature of the capping agent produced significantly relies on the final application of QDs. Frequently used ligands in QDs synthesis are alcohols, essential amines, and thiols [18, 19]. Bio-conjugation with carbohydrates, viruses, natural products, DNA fragments, and peptides assist by ligands through the covalent coupling and electrostatic or hydrophobic interactions [20, 21]. Determination of solubility, colloidal stability, control particle morphology, particle size distribution, and accumulation chiefly depends on ligands [22–24]. The present work aims to cover the optical properties, method of preparations, surface modifications, bio-conjugation, characterization, stability, and cytotoxicity of QDs. Articles were reviewed in English literature reporting the pharmaceutical and bio-pharmaceutical aspects of QDs which were indexed in Scopus, web of science, google scholar and PubMed without applying the year of publication criterion. The keywords used for searching the literature are quantum dots, quantum dots in drug delivery system, methods of preparation of quantum dots, applications of quantum dots, recent advances in quantum dots, pharmaceutical and biopharmaceutical applications of quantum dots etc. QDs core consists of several substances like cadmium, zinc, lead chalcogenides (CdS, CdSe, CdTe), copper salt (CuCl), arsenides (InAs, GaAs), semiconducting phosphides (InP, GaP), and nitrides (GaN). The shell of CdSe, ZnSe, PbS, ZnS, ZnTe, CdS, ZnO generally enclosed the core [3]. The core of nanomaterials guarded by outer covering from photoinitiated degradation and removing surface defects enhances the luminescence properties. Besides, cadmium, silver, copper, manganese, and rare earth metal ions can be used to dope the core of nanocrystals to enhance photoluminescence properties [25, 26]. QDs can be assembled, permitting particle shape, size, and chemical composition to be changed by suit a given application. The design and size of QDs are the properties that are frequently manipulated; this will decide if the QDs are chemically excited in NIR or UV light [27–29]. The biological targeting molecules (e. g., antibodies) or biocompatible polymeric materials (e. g., PEG) can be functionalized on the amenable external surface of QDs to improve their physiological system performance. The most commonly utilized QDs consist of graphene QDs, carbon QDs, and cadmium- based QDs [30–32]. QDs are found to be photochemically stable with symmetric, narrow, and strong fluorescence emission. QDs are International Journal of Applied Pharmaceutics ISSN- 0975-7058 Vol 13, Issue 5, 2021