George Mattheolabakis

Nanodelivery strategies in cancer chemotherapy: biological rationale and pharmaceutical perspectives

Nanotechnology is revolutionizing our approach to drug delivery, a key determinant of drug efficacy. Here, we present cancer drug delivery strategies that exploit nanotechnology, providing first an overview of tumor biology aspects that critically affect the design of drug delivery carriers, namely the enhanced permeability and retention effect, the lower tumor extracellular pH and tumor-specific antigens. In general, nanoscience-based approaches have circumvented limitations in the delivery of cancer therapeutics, related to their poor aqueous solubility and toxicity issues with conventional vehicles and resulted in improved pharmacokinetics and biodistribution. Included in the discussion are promising examples and pharmaceutical perspectives on liposomes, nanoemulsions, solid lipid nanoparticles, polymeric nanoparticles, dendrimers, carbon nanotubes and magnetic nanoparticles. As the cardinal features of the ideal multifunctional cancer drug nanocarrier are becoming clear, and drug development challenges are proactively addressed, we anticipate that future advances will enhance therapeutic outcomes by refining the delivery and targeting of complex payloads.

Hyaluronic acid targeting of CD44 for cancer therapy: from receptor biology to nanomedicine

Abstract Cluster of differentiation-44 (CD44) is a ubiquitously present glycoprotein on the surface of mammalian cells that plays a significant role in a number of biological functions. Since the discovery that the receptor is over-expressed in a variety of solid tumors, such as pancreatic, breast and lung cancer, many studies have focused on methods for targeting CD44 in an attempt to improve drug delivery and discrimination between healthy and malignant tissue, while reducing residual toxicity and off-target accumulation. In this review, we describe CD44 receptor biology and its involvement in the different stages of tumor growth and metastasis, as well as methods currently used for targeting the receptor. Hyaluronic acid, the primary CD44 binding molecule, has proved a significant ally in developing nanocarriers that demonstrate preferential tumor accumulation and increased cell uptake. We outline a number of research approaches from the current literature that take advantage of hyaluronic acid’s targeting ability and describe the possible advantages for each approach. The value of CD44 targeting can be easily appreciated from the number of different approaches that have reached clinical trials.

In vivo investigation of tolerance and antitumor activity of cisplatin-loaded PLGA-mPEG nanoparticles.

The tolerance of BALB/c mice to different doses of blank and cisplatin-loaded PLGA-mPEG nanoparticles and the in vivo anticancer activity of these nanoparticles on SCID mice xenografted with colorectal adenocarcinoma HT 29 cells were investigated. Nanoparticles with an average size of 150-160 nm and approximately 2% w/w cisplatin content were prepared by a modified emulsification and solvent evaporation method. Normal BALB/c mice tolerated three weekly intravenous injections of a relatively high dose of blank PLGA-mPEG nanoparticles (500 mg/kg, equivalent to about 10mg nanoparticles/mouse) and three weekly intravenous injections of a high dose of nanoparticle-entrapped cisplatin (10 mg/kg). Also, histopathology examination indicated that there were no differences in the kidneys or spleens from animals treated with cisplatin-loaded nanoparticles or blank nanoparticles compared to the untreated control group. A moderate granulation of protoplasm of hepatic cells was observed in the livers from mice treated with cisplatin-loaded nanoparticles and blank nanoparticles, however, both the hepatic lobe and the portal hepatis maintained their normal architecture. The cisplatin-loaded PLGA-mPEG nanoparticles appeared to be effective at delaying tumor growth in HT 29 tumor-bearing SCID mice. The group of mice treated with cisplatin-loaded nanoparticles exhibited higher survival rate compared to the free cisplatin group. The results justify further evaluation of the in vivo antitumor efficacy of the PLGA-mPEG/cisplatin nanoparticles.

Transcutaneous delivery of a nanoencapsulated antigen: Induction of immune responses

We investigated the influence of antigen entrapment in PLA nanoparticles on the immune responses obtained after transcutaneous immunization. OVA-loaded PLA nanoparticles were prepared using a double emulsion process. Following application onto bare skin of mice in vivo, fluorescence-labeled nanoparticles were detected in the duct of the hair follicles indicating that the nanoparticles can penetrate the skin barrier through the hair follicles. Although the OVA-loaded nanoparticles elicited lower antibody responses than those induced by OVA in aqueous solution they were more efficient in inducing cytokine responses. In vitro re-stimulation of cultured splenocytes with OVA elicited a little higher levels of IFN-gamma (difference statistically insignificant, p>0.05) and significantly higher levels of IL-2 (p<0.001) in mice immunized with OVA-loaded nanoparticles compared to those immunized with OVA in solution. In the presence of CT, the OVA-loaded nanoparticles induced significantly higher IFN-gamma and IL-2 than all other formulations. Transcutaneous administration of OVA encapsulated in the PLA nanoparticles exhibited priming efficacy to a challenging dose of OVA given via different route. These findings indicate the potential of nanoparticles to deliver antigens via the transcutaneous route and prime for antibody and strong cellular responses. The co-administration of an adjuvant such as CT had the added advantage of modulating the immune response, a desirable characteristic within the context of vaccination against intracellular versus extracellular pathogens.

Targeting Mitochondrial STAT3 with the Novel Phospho-Valproic Acid (MDC-1112) Inhibits Pancreatic Cancer Growth in Mice

New agents are needed to treat pancreatic cancer, one of the most lethal human malignancies. We synthesized phospho-valproic acid, a novel valproic acid derivative, (P-V; MDC-1112) and evaluated its efficacy in the control of pancreatic cancer. P-V inhibited the growth of human pancreatic cancer xenografts in mice by 60%–97%, and 100% when combined with cimetidine. The dominant molecular target of P-V was STAT3. P-V inhibited the phosphorylation of JAK2 and Src, and the Hsp90-STAT3 association, suppressing the activating phosphorylation of STAT3, which in turn reduced the expression of STAT3-dependent proteins Bcl-xL, Mcl-1 and survivin. P-V also reduced STAT3 levels in the mitochondria by preventing its translocation from the cytosol, and enhanced the mitochondrial levels of reactive oxygen species, which triggered apoptosis. Inhibition of mitochondrial STAT3 by P-V was required for its anticancer effect; mitochondrial STAT3 overexpression rescued animals from the tumor growth inhibition by P-V. Our results indicate that P-V is a promising candidate drug against pancreatic cancer and establish mitochondrial STAT3 as its key molecular target.

Exosomes as nanocarriers for immunotherapy of cancer and inflammatory diseases.

Cell secreted exosomes (30-100nm vesicles) play a major role in intercellular communication due to their ability to transfer proteins and nucleic acids from one cell to another. Depending on the originating cell type and the cargo, exosomes can have immunosuppressive or immunostimulatory effects, which have potential application as immunotherapies for cancer and autoimmune diseases. Cellular components shed from tumor cells or antigen presenting cells (APCs), such as dendritic cells, macrophages and B cells, have been shown to be efficiently packaged in exosomes. In this review, we focus on the application of exosomes as nanocarriers and immunological agents for cancer and autoimmune immunotherapy. APC-derived exosomes demonstrate effective therapeutic efficacy for the treatment of cancer and experimental autoimmune diseases such as rheumatoid arthritis, inflammatory bowel disease, and multiple sclerosis. In addition to their intrinsic immunomodulating activity, exosomes have many advantages over conventional nanocarriers for drug and gene delivery.

Effect of Conditions of Preparation on the Size and Encapsulation Properties of PLGA-mPEG Nanoparticles of Cisplatin

The effect of conditions of preparation on the size and encapsulation properties of PLGA-mPEG nanoparticles of cisplatin was investigated. A modified double emulsion method was applied for the preparation of PLGAmPEG nanoparticles of cisplatin, based on the partial or complete replacement of the water of the inner aqueous phase of the emulsion by dimethyl formamide(dmf) or the addition of cisplatin in the form of a complex with poly(glutamic acid). These modifications resulted in significant improvement of cisplatin loading in the PLGA-mPEG nanoparticles. Increased cisplatin loading and encapsulation efficiency were obtained when a relatively low dmf/water ratio, low dmf volume (when pure dmf formed the inner polar phase), or a high drug/polymer ratio were applied. A reduction of average size of nanoparticles was observed with decreasing the amount of PLGA-mPEG added in the formulation or increasing sonication time. The only factor that had a significant effect on size distribution was the sonication time, with the size P.I. being decreased with increasing sonication time. Prolonged sonication, however, decreased cisplatin loading and encapsulation efficiency. From the four lyoprotectant sugars tested (glucose, lactose, mannitol, and trehalose), only mannitol could prevent nanoparticle aggregation upon lyophilization. When appropriate amounts of an effective lyoprotectant were added in nanoparticles before lyophilization, drug loading of the nanoparticles was not affected by nanoparticle lyophilization.

Self-assembly and drug delivery studies of pH/thermo-sensitive polyampholytic (A-co-B)-b-C-b-(A-co-B) segmented terpolymers

We investigated the behavior of the pH and thermo-responsive poly(2-(diethylamino)ethyl methacrylate-co-methacrylic acid)-b-(ethylene glycol methyl ether methacrylate)-b-poly(2-(diethylamino)ethyl methacrylate-co-methacrylic acid) (P(DEAEMA-co-MAA)-b-PEGMA-b-P(DEAEMA-co-MAA)) triblock terpolymers in aqueous solution by means of static and dynamic light scattering, transmission electron microscopy and rheology. Association phenomena were observed at the isoelectric point region of the polyampholyte outer blocks leading to flower-like micelles and at higher polymer concentrations, to a three dimensional transient micellar network, exhibiting a compex thermo-response thanks to the thermo-sensitivity of the PEGMA middle block. Doxorubicin (DOX) drug was loaded in the terpolymer micelles and drug release studies were performed. Controlled drug delivery could be achieved by tuning pH. The terpolymer micelles exhibited satisfactory cytocompatibility towards human umbilical vein endothelial cells.

Facile synthesis of polyester-PEG triblock copolymers and preparation of amphiphilic nanoparticles as drug carriers.

Novel amphiphilic triblock copolymers of poly(propylene succinate) (PPSu) and poly(ethylene glycol) (PEG) with different hydrophobic/hydrophilic ratios were synthesized using a facile one-pot procedure. The molecular weight of the copolymers was adjusted by varying the molecular weight of PPSu while keeping that of PEG constant. The copolymers exhibited glass transition temperatures between -36.0 and -38°C and single melting points around 44°C. WAXD data indicated that both blocks of the copolymers could crystallize. The mPEG-PPSu copolymers exhibited low in vitro toxicity against HUVEC cells. The synthesized copolymers were used to prepare core-shell nanoparticles with hydrophobic PPSu and hydrophilic PEG forming the core and shell, respectively. The drug loading efficiency and drug release properties of the mPEG-PPSu nanoparticles were investigated using two model drugs: the hydrophilic Ropinirole and the hydrophobic Tibolone. The mean size of the drug-loaded mPEG-PPSu nanoparticles ranged between 150 and 300nm and increased with the molecular weight of the PPSu block. The drug loading efficiency of the nanoparticles was found to be dependent upon drug hydrophilicity and was much higher for the hydrophobic Tibolone. Drug release characteristics also depended on drug hydrophilicity: the hydrophilic Ropinirole was released at a much higher rate than the hydrophobic Tibolone. Contrary to Ropinirole, the profiles of Tibolone exhibited an early phase of burst release followed by a phase of slow release. By varying the composition (mPEG/PPSu ratio) of mPEG-PPSU copolymers, nanoparticles of different sizes and drug loading capacities can be synthesized exhibiting different drug release characteristics. Based on the results obtained, the proposed mPEG-PPSu copolymers can be useful in various controlled drug delivery applications, especially those involving relatively hydrophobic drugs.

Mixed Nanosized Polymeric Micelles as Promoter of Doxorubicin and miRNA-34a Co-Delivery Triggered by Dual Stimuli in Tumor Tissue.

Dual stimuli-sensitive mixed polymeric micelles (MM) are developed for co-delivery of the endogenous tumor suppressor miRNA-34a and the chemotherapeutic agent doxorubicin (Dox) into cancer cells. The novelty of the system resides in two stimuli-sensitive prodrugs, a matrix metalloproteinase 2 (MMP2)-sensitive Dox conjugate and a reducing agent (glutathione, GSH)-sensitive miRNA-34a conjugate, self-assembled in a single particle decorated with a polyethylene glycol corona for longevity, and a cell-penetrating peptide (TATp) for enhanced intracellular delivery. The MMP2-sensitivity of the system results in threefold higher cytotoxicity in MMP2-overexpressing HT1080 cells compared to low MMP2-expressing MCF7 cells. Cellular internalization of Dox increases by more than 70% after inclusion of TATp to the formulation. MMP2-sensitive MM also inhibits proliferation and migration of HT1080 cells. Moreover, GSH-sensitive MM allows for an efficient downregulation of Bcl2, survivin, and notch1 (65%, 55%, and 46%, respectively) in HT1080 cells. Combination of both conjugates in dual sensitive MM reduces HT1080 cell viability to 40% and expression of Bcl2 and survivin. Finally, 50% cell death is observed in 3D models of tumor mass. The results confirm the potential of the MM to codeliver miRNA-34a and doxorubicin triggered by dual stimuli inherent of tumor tissues.