Journal of Analytical & Pharmaceutical Research Quantum Dots in Photodynamic Therapy for Cancer Abstract Opinion Photodynamic therapy (PDT) is a promising, non-invasive therapeutic approach. Volume 3 Issue 2 - 2016 PDT involves Photosensitizer (PS) drugs and an external light source is the essential components of PDT and cytotoxic reactive oxygen species are generated that destroys cancer cells. Despite of a new potential anticancer therapeutic strategy, success of PDT is limited due to low water solubility of photosensitizers National Chemical Laboratory, Organic Chemistry Division, India which limits the wide applicability of these molecules. Nano-platforms based on PS incorporated in nanomaterials can be applied for targeted PDT with reduced *Corresponding author: Preeti Nigam Joshi, National side effects and better efficiency. This article provides an insight on few recent Chemical Laboratory, Organic Chemistry Division, Pune- advancements of quantum dots based PDT and future aspects. 411008, India, Tel: +91-20-2590-2443; E-mail: Keywords: Photodynamic therapy; Nanotechnology; Quantum dots; Cancer; Photosensitizers; Nano-platforms Received: September 27, 2016 | Published: October 07, 2016 Abbreviations: PDT: Photodynamic Therapy; PS: procedures with relatively short span of side effects as compare to Photosensitizer; NIR: Near Infra Red; ALA: Aminolevulinic chemotherapy or radiotherapy. Based on its mode of action, it also Acid; MAOP: Methyl Aminolevulinate; BRET: Bioluminescence annihilates the vasculature associated with the tumor besides the Resonance Energy Transfer Furthermore, PDT is a localized therapy and can be directed to Introduction atumor target itself, tissue which very preciselycontributes as significantlyonly the irradiated to tumor area death receives [7]. the PS and the light simultaneously. Another important feature of From ancient Egypt civilization, light and chemicals in PDT is, it’s cost effective and can be repeated several times at one combination are being used for therapeutic purposes like location if necessary without leaving any scar, a major limiting treatment of psoriasis and vitiligo [1]. However, modern PDT factor with radiation [6]. Despite of several advantages and a was discovered by Raab, Tappeiner, Huang [2-4] in the beginning better alternative of conventional chemotherapy approaches, of 20th century. The principal of PDT involves light activation of PDT has its own set of draw backs like mostly photosensitizers are less water soluble that prevents their effective utilization, it’s a light dependent technique and for deep tissue penetration oxygensome specific (1O ) that kind is deleteriousof chemicals to cells.called Cancer photosensitizers is still the most(PS) 2 like treatment of lung. liver, pancreatic cancers, a PS excitation fatalthat diseasegenerates that reactive claims manyoxygen life species;world-wide specifically every year singlet and wavelengths should fall in near infra red (NIR) and it’s the need of despite of tremendous medical advancements no cure has been hour to develop new PS with their optical properties as require as found for this disease and chemotherapy; the most explored to date PDT has mostly applied for skin cancers only. Moreover, PDT treatment option is also not effective in many cases. In this regard can’t be applied for metastatic cancers as it’s a localized therapy. alternative therapy approaches are a must and PDT is the most Oxygenation of tumor and tissues is required for the effective suitable and effective alternative of conventional therapies. The photodynamic therapy as tumors surrounded by necrotic tissue prime components of any PDT are: a photosensitizer (PS), a light source, and oxygen. This approach is distinct from laser-activated granted FDA approvals like sodium (Photofrin), 5-aminolevulinic photothermal approaches where high intensity pulsed lasers acidor intense or ALA tumor (Levulan), masses impedeand methyl PDT efficacy. aminolevulinate Many PS have [MAOP] been are used to generate thermal effects, while in PDT typically low (Metvix) and research is going on for its wider applicability for irradiances in the mW/cm2 ranges are required and instead of other cancers also [6,8]. thermally induced tissue burning, PDT is a gentle approach where dose depends on the induced photochemistry with no alternation Nanotechnology Intervention and quantum dots: New in biological activity after removal of light source [4]. paradigm for PDT Advantages and Limitations of PDT PDT has several advantages over conventional cancer treatment approaches. Firstly, it has no long-term side effects sciencesNanotechnology also witnessed is a trulythe deep revolutionary impact of field nanotechnology of modern era in thethat areahas ofinfluenced drug delivery almost and every diagnostics research where arena a newand medicalbranch- self-limited photosensitivity to the eyes and skin was observed ‘nanotheranostics’ has been evolved. PDT has also been greatly [5,6].when PDTproperly procedures used although, are most oftenwith firstperformed generation on an PSs, outpatient minor basis and it is a less invasive technique as compare to surgical lipid, metallic nanoparticles and quantum dots have seen vast benefited by nanotechnology and nano based liposomal, Submit Manuscript | http://medcraveonline.com J Anal Pharm Res 2016, 3(2): 00055 Copyright: Quantum Dots in Photodynamic Therapy for Cancer ©2016 Joshi 2/3 applications in recent years that have enriched the potential the prime hurdle is release of Cd+2 due to colloidal instability in approval of PDT was given to Visudyne® subsequent generation of radicals and malfunction of cellular formulation,of this alternate and redtherapy light for for the cancer. treatment In 2001, of age-related the first macular clinical organellesbody fluids likethat isdisruption extremely of toxic plasma for in membrane, vivo application nuclei due and to degeneration [9]. In combination with, a nanotechnology,liposomal verteporfin PDT mitochondria [19,20]. To prevent the toxicity of semiconductor provides brilliant opportunities for therapeutic agents delivery quantum dots, approaches like QD core and polymer shell types and newer approaches for photomedicine. The major advantages structures have been adopted. But the systematic evaluation of of nano-PDT include enhanced PS delivery to target site, circulation time and deterioration of shell that would release the QD hasn’t been evaluated fully which limits the wide acceptability of novel light sources, personalized predictive dosimetry and of these materials in PDT. However QDs of graphene and other advancementmodification ofof PScombinatorial physiochemical therapeutic properties, approaches and development [4]. carbon materials are more biocompatible and exhibit similar properties like their semi conductor counterparts. Due to their Although various nanoparticles have been applied but quantum dots (QDs) - tiny nanoparticles of semiconductors or substitute than the former semiconductor QDs. less toxicity and ease of surface modification, these are better excellent size tunable optical properties, needed for effective PDT PDT is a potential alternate of traditional chemotherapy but ingraphene/carbon deep tissue cancers. size ≤ QDs20 nmhave are their rather typical special photoluminance due to their few drawbacks like low water solubility of photosensitizer drugs, property and can be tuned for excitation at NIR wavelengths also that makes them excellent entities for their application in PDT. properties of PS in NIR regions for better penetration for deep QDs are superior to conventional PS in terms of photostability tissuelack of cancers, targeted limits delivery its wideat tumor applicability. site and desiredThe rise fluorescence of QDs has and water dispersiblity [10,11]. Despite of these advantages, cytotoxicity and less ROS generation has impaired the clinical utility of these agents. Therefore, alternate approaches like opened new avenues in PDT and with the flexibility of surface modifications to enhance biocompatibility and optoelectrical (porphyrin derivative, Ce6) have been designed to mitigate the modulation; these new materials have significantly enrich the In recent years, many QDs based nanoconjugates for PDT have cytotoxicitysurface modified with QDsenhanced conjugated ROS generation. with a traditional Moreover, PDT another agent field of PDT. been reported and the encouraging results indicate bright future of strategy of QDs driven PDT based on Forster resonance energy such alternate approaches to overcome the limitations of existing transfer (FRET) has also been proposed. Owing to their distinctive photodynamic therapy. QDs due to their excellent opto-electrical optical and spectroscopic properties of tunable emission spectra, choice for PDT applications and with involvement of FRET /BRET are ideal donors/ acceptors for FRET and can be explored for mechanismproperties, easyare good surface alternatives modification of other techniques nanomaterials. are a preferred In a nut eitherhigh molar via FRET extinction or direct coefficient electron and transfer high PL to quantum oxygen moleculesyield, QDs shell it can be concluded that although in nascent stage, these small nano entities holds lots of potential and we can expect their by Burda et al. also in their study, evaluating interaction of CdSe QDsfor generation with a silicon of ROS phthalocyanine in PDT [12]. PSSimilar (Pc4) findings [13]. Bioluminescence were reported resonance energy transfer (BRET); an