Nano-systems of a curcumin derivative for cancer therapy

Abstract

For centuries, crude CUR was used as food spice and dietary supplement, in addition to traditional Asian medicine. Commercial turmeric extract contains structurally-related curcuminoids; 75% diferuloylmethane/curcumin (curcumin I), 20% demethoxycurcumin (curcumin II), 5% bisdemethoxycurcumin BDMC (curcumin III). CUR gained immense popularity in the last decade with around 8400 hits on PubMed on usage of “curcumin” as the search string; possibly as a ‘next-generation multipurpose drug’ due to its widespread applicability in prophylaxis and treatment of various pro-inflammatory chronic diseases, including neurodegenerative diseases, cardiovascular, pulmonary, metabolic and many other diseases. Moreover, recently CUR anti-cancer activity has been extensively investigated and supporting evidences were found for its potential use in chemoprevention and treatment of a wide variety of tumors; including head and neck, lung, colorectal, breast, GIT, genitourinary, melanoma, neurological and sarcoma. Curcumin exerts its anti-cancer effect by various mechanisms; including: activating apoptosis signaling and inhibiting cell proliferation as it inhibits Bcl2 and activates Caspase 9 to induce apoptosis, also it inhibits many signaling pathways for tumour cell proliferation such as MAP kinase pathway, AKT pathway and mTOR pathways. Moreover, it inhibits inflammatory cytokines (TNFα, Interleukins & multiple protein kinases). CUR delivery faces some challenges owing to their poor aqueous solubility, photodegradation, chemical instability, poor bioavailability and rapid metabolism in vivo. Interestingly, curcumin III (Bisdemethoxycurcumin) (BDMC) which is the bisdemethoxylated derivative of curcumin was found to possess enhanced anti-cancer potency yet more hydrophobicity. Accordingly, its main delivery problem lies in its extreme poor aqueous solubility. Currently, BDMC is under extensive research for enhancing its targeted delivery to cancer cells and improving its poor solubility. Nanotechnology is considered the cutting edge of biomaterials research and the science of future. Nano-systems gained widespread popularity because of their potential to enhance the biological effect of incorporated drugs possibly by protecting drugs from enzymatic degradation, providing controlled release, altering their pharmacokinetics and prolonging their residence in plasma, decreasing their toxicity and limiting nonspecific uptake to undesirable tissues. Additionally, among the various applications of nanotechnology is enhancement of aqueous solubility of lipophilic drugs like CUR and maximization of its bioavailability and tissue biodistribution in drug delivery systems. These nano-systems take the advantage of the unique properties of malignant tissues to deliver chemotherapy specifically towards solid tumors and spare normal cells with maximized therapeutic efficiency and minimized side effects. This gold standard in Passive cancer targeting identified as EPR (Enhanced Permeability and Retention) coined by Maeda and Matsumura back in 1986, depends on the characteristic properties of tumour vasculature which are: (1) Highly defective architecture of blood vessels with elevated levels of permeability factors, to afford sufficient nutrients and oxygen for rapid tumour growth (2) Manifested large endothelial cell-cell gap openings (3) Highly impaired lymphatic drainage from tumor tissue. All these factors support leakage of macromolecules (above 40 kDa) outside vessels and their selective accumulation in tumour cells while having limited access to normal organs because of their tightly-knitted endothelial lining. Therefore, the aim of this thesis was to formulate and prepare BDMC-loaded nanosystems, mixed micelles and polymeric nanoparticles, dedicated to improve its aqueous solubility, passive targeting and reduced untoward side effects for cancer therapy. Hence the work in this thesis was divided into two chapters: 1- Chapter I: Preparation and evaluation of BDMC-loaded Pluronic mixed micelles. 2- Chapter II: Preparation and evaluation of BDMC-loaded PLGA nanoparticles.

Chapter I: Preparation and evaluation of BDMC-loaded Pluronic mixed micelles In this chapter, BDMC-loaded Pluronic mixed micelles were prepared adopting thin-film hydration technique. The mixed micelles were prepared according to a full factorial design to study the effect of two independent variables, namely the ratio of Pluronics® used (F68%:F127%) at 3 levels: 15:85, 20:80 and 25:75, and ratio of organic solvent utilized in micellar thin film preparation (Acetone%: Acetonitrile %) at 3 levels (100:0, 50:50, 0:100) leading to preparation of 9 (32) formulations. Whereas, the dependent variables (responses) were the particle size (PS), polydispersity index (PDI), zeta potential (ZP), and entrapment efficiency (EE %). The values of critical micelle concentration (CMC) of the used Pluronics were determined via pyrene fluorescence method, as 0.25 mg/ml (2.994 10-5 M) and 0.1 mg/ml (7.93 10-6 M) for F68 and F127, respectively. The calculated CMC for mixed micellar formulations were around 1 10-5 M, according to the simplified equation of Markov chain model of mixed surfactant systems which confirms high thermodynamic stability of the prepared micelles, as well as expected in-vivo longevity even with many fold dilution within plasma.