Mario Sechi

Targeted therapy using nanotechnology: focus on cancer.

Recent advances in nanotechnology and biotechnology have contributed to the development of engineered nanoscale materials as innovative prototypes to be used for biomedical applications and optimized therapy. Due to their unique features, including a large surface area, structural properties, and a long circulation time in blood compared with small molecules, a plethora of nanomaterials has been developed, with the potential to revolutionize the diagnosis and treatment of several diseases, in particular by improving the sensitivity and recognition ability of imaging contrast agents and by selectively directing bioactive agents to biological targets. Focusing on cancer, promising nanoprototypes have been designed to overcome the lack of specificity of conventional chemotherapeutic agents, as well as for early detection of precancerous and malignant lesions. However, several obstacles, including difficulty in achieving the optimal combination of physicochemical parameters for tumor targeting, evading particle clearance mechanisms, and controlling drug release, prevent the translation of nanomedicines into therapy. In spite of this, recent efforts have been focused on developing functionalized nanoparticles for delivery of therapeutic agents to specific molecular targets overexpressed on different cancer cells. In particular, the combination of targeted and controlled-release polymer nanotechnologies has resulted in a new programmable nanotherapeutic formulation of docetaxel, namely BIND-014, which recently entered Phase II clinical testing for patients with solid tumors. BIND-014 has been developed to overcome the limitations facing delivery of nanoparticles to many neoplasms, and represents a validated example of targeted nanosystems with the optimal biophysicochemical properties needed for successful tumor eradication.

Graphene-containing thermoresponsive nanocomposite hydrogels of poly(N-isopropylacrylamide) prepared by frontal polymerization

Frontal polymerization has been successfully used to synthesize poly(N-isopropylacrylamide) nanocomposite hydrogels containing graphene. The latter was directly achieved by ultrasound treatment of a dispersion of graphite in N-methylpyrrolidone. The dispersion, having the concentration of 2.21 g L−1, was characterized by TEM analysis and mixed with suitable amounts of N-isopropylacrylamide for the synthesis of graphene-containing nanocomposite polymer hydrogels. The nanocomposite hydrogels were analyzed by SEM and Raman spectroscopy, and their swelling and rheological properties were investigated. It was found that graphene strongly influences the swelling ratio, dramatically increasing it, even if present in small amounts. Finally, the rheological properties of the hydrogels were correlated with the graphene content: G′ modulus and complex viscosity were found to increase with increasing nanofiller concentration, thus indicating the occurrence of good interactions between the two phases. Nevertheless, at a high concentration (i.e., 0.13 wt.%), graphene showed a lubrication effect, lowering the rheological parameters and approaching the same pseudoplastic behaviour of the unfilled material.

Development of novel cationic chitosan-and anionic alginate–coated poly(d,l-lactide-co-glycolide) nanoparticles for controlled release and light protection of resveratrol

Background Resveratrol, like other natural polyphenols, is an extremely photosensitive compound with low chemical stability, which limits the therapeutic application of its beneficial effects. The development of innovative formulation strategies, able to overcome physicochemical and pharmacokinetic limitations of this compound, may be achieved via suitable carriers able to associate controlled release and protection. In this context, nanotechnology is proving to be a powerful strategy. In this study, we developed novel cationic chitosan (CS)- and anionic alginate (Alg)-coated poly(d,l-lactide-co-glycolide) nanoparticles (NPs) loaded with the bioactive polyphenolic trans-(E)-resveratrol (RSV) for biomedical applications. Methods NPs were prepared by the nanoprecipitation method and characterized in terms of morphology, size and zeta potential, encapsulation efficiency, Raman spectroscopy, swelling properties, differential scanning calorimetry, and in vitro release studies. The protective effect of the nanosystems under the light-stressed RSV and long-term stability were investigated. Results NPs turned out to be spherical in shape, with size ranging from 135 to about 580 nm, depending on the composition and the amount of polyelectrolytes, while the encapsulation efficiencies increased from 8% of uncoated poly(d,l-lactide-co-glycolide) (PLGA) to 23% and 32% of Alg- and CS-coated PLGA NPs, respectively. All nanocarriers are characterized by a biphasic release pattern, and more effective controlled release rates are obtained for NPs formulated with higher polyelectrolyte concentrations. Stability studies revealed that encapsulation provides significant protection against light-exposure degradation, by reducing the trans–cis photoisomerization reaction. Moreover, the nanosystems are able to prevent the degradation of trans isoform and the leakage of RSV from the carrier for a period of 6 months. Conclusion Our findings indicated that the newly developed CS- and Alg-coated PLGA NPs are suitable to be used for the delivery of bioactive RSV. The encapsulation of RSV into optimized polymeric NPs provides improved drug loading, effective controlled release, and protection against light-exposure degradation, thus opening new perspectives for the delivery of bioactive related phytochemicals to be used for (nano)chemoprevention/chemotherapy.

Novel docetaxel-loaded nanoparticles based on poly(lactide-co-caprolactone) and poly(lactide- co-glycolide-co-caprolactone) for prostate cancer treatment: formulation, characterization, and cytotoxicity studies

Docetaxel (Dtx) chemotherapy is the optional treatment in patients with hormone-refractory metastatic prostate cancer, and Dtx-loaded polymeric nanoparticles (NPs) have the potential to induce durable clinical responses. However, alternative formulations are needed to overcome the serious side effects, also due to the adjuvant used, and to improve the clinical efficacy of the drug.In the present study, two novel biodegradable block-copolymers, poly(lactide-co-caprolactone) (PLA-PCL) and poly(lactide-co-caprolactone-co-glycolide) (PLGA-PCL), were explored for the formulation of Dtx-loaded NPs and compared with PLA- and PLGA-NPs. The nanosystems were prepared by an original nanoprecipitation method, using Pluronic F-127 as surfactant agent, and were characterized in terms of morphology, size distribution, encapsulation efficiency, crystalline structure, and in vitro release. To evaluate the potential anticancer efficacy of a nanoparticulate system, in vitro cytotoxicity studies on human prostate cancer cell line (PC3) were carried out. NPs were found to be of spherical shape with an average diameter in the range of 100 to 200 nm and a unimodal particle size distribution. Dtx was incorporated into the PLGA-PCL NPs with higher (p < 0.05) encapsulation efficiency than that of other polymers. Differential scanning calorimetry suggested that Dtx was molecularly dispersed in the polymeric matrices. In vitro drug release study showed that release profiles of Dtx varied on the bases of characteristics of polymers used for formulation. PLA-PCL and PLGA-PCL drug loaded NPs shared an overlapping release profiles, and are able to release about 90% of drug within 6 h, when compared with PLA- and PLGA-NPs. Moreover, cytotoxicity studies demonstrated advantages of the Dtx-loaded PLGA-PCL NPs over pure Dtx in both time- and concentration-dependent manner. In particular, an increase of 20% of PC3 growth inhibition was determined by PLGA-PCL NPs with respect to free drug after 72 h incubation and at all tested Dtx concentration. In summary, PLGA-PCL copolymer may be considered as an attractive and promising polymeric material for the formulation of Dtx NPs as delivery system for prostate cancer treatment, and can also be pursued as a validated system in a more large context.

Resveratrol-Loaded Nanoparticles Based on Poly(epsilon-caprolactone) and Poly(d,l-lactic-co-glycolic acid)–Poly(ethylene glycol) Blend for Prostate Cancer Treatment

Nanoencapsulation of antiproliferative and chemopreventive phytoalexin trans-resveratrol (RSV) is likely to provide protection against degradation, enhancement of bioavailability, improvement in intracellular penetration and control delivery. In this study, polymeric nanoparticles (NPs) encapsulating RSV (nano-RSV) as novel prototypes for prostate cancer (PCa) treatment were designed, characterized and evaluated using human PCa cells. Nanosystems, composed of a biocompatible blend of poly(epsilon-caprolactone) (PCL) and poly(d,l-lactic-co-glycolic acid)-poly(ethylene glycol) conjugate (PLGA-PEG-COOH), were prepared by a nanoprecipitation method, and characterized in terms of morphology, particle size and zeta potential, encapsulation efficiency, thermal analyses, and in vitro release studies. Cellular uptake of NPs was then evaluated in PCa cell lines DU-145, PC-3, and LNCaP using confocal fluorescence microscopy, and antiproliferative efficacy was assessed using MTT assay. With encapsulation efficiencies ranging from 74% to 98%, RSV was successfully loaded in PCL:PLGA-PEG-COOH NPs, which showed an average diameter of 150 nm. NPs were able to control the RSV release at pH 6.5 and 7.4, mimicking the acidic tumoral microenvironment and physiological conditions, respectively, with only 55% of RSV released within 7 h. In gastrointestinal simulated fluids, NPs released about 55% of RSV in the first 2 h in acidic medium, and their total RSV content within the subsequent 5 h at pH 7.4. Confocal fluorescence microscopy observations revealed that NPs were efficiently taken up by PCa cell lines. Furthermore, nano-RSV significantly improved the cytotoxicity compared to that of free RSV toward all three cell lines, at all tested concentrations (from 10 μM to 40 μM), proving a consistent sensitivity toward both the androgen-independent DU-145 and hormone-sensitive LNCaP cells. Our findings support the potential use of developed nanoprototypes for the controlled delivery of bioactive RSV for PCa chemoprevention/chemotherapy.

Nanoparticle therapeutics for prostate cancer treatment

The application of nanotechnology in medicine is offering many exciting possibilities in healthcare. Engineered nanoparticles have the potential to revolutionize the diagnosis and the therapy of several diseases, particularly by targeted delivery of anticancer drugs and imaging contrast agents. Prostate cancer, the second most common cancer in men, represents one of the major epidemiological problems, especially for patients in the advanced age. There is a substantial interest in developing therapeutic options for treatment of prostate cancer based on use of nanodevices, to overcome the lack of specificity of conventional chemotherapeutic agents as well as for the early detection of precancerous and malignant lesions. Herein, we highlight on the recent development of nanotechnology strategies adopted for the management of prostate cancer. In particular, the combination of targeted and controlled-release polymer nanotechnologies has recently resulted in the clinical development of BIND-014, a promising targeted Docetaxel-loaded nanoprototype, which can be validated for use in the prostate cancer therapy. However, several limitations facing nanoparticle delivery to solid tumours, such as heterogeneity of intratumoural barriers and vasculature, cytotoxicity and/or hypersensitivity reactions to currently available cancer nanomedicines, and the difficult in developing targeted nanoparticles with optimal biophysicochemical properties, should be still addressed for a successful tumour eradication.

Development of polymeric microbubbles targeted to prostate-specific membrane antigen as prototype of novel ultrasound contrast agents.

Ultrasound-targeted microbubbles (MBs) offer new opportunities to enhance the capabilities of diagnostic ultrasound (US) imaging to specific pathological tissue. Herein, we report on the design and development of a novel prototype of US contrast agent based on polymeric MBs targeted to prostate-specific membrane antigen (PSMA) for use in the diagnosis of prostate cancer (PCa). First, a set of air-filled MBs by a variety of biocompatible polymers were prepared and characterized in terms of morphology and echogenic properties after exposure to US. MBs derived from poly(D,L-lactic-co-glycolic acid) (PLGA)-poly(ethylene glycol) (PEG) copolymer resulted as the most effective in terms of reflectivity. Such polymer was therefore preconjugated with a urea-based PSMA inhibitor molecular probe (DCL), and the obtained MBs were investigated in vitro for their targeting efficacy toward PSMA positive PCa (LNCaP) cells. Fluorescence microscopy proved a specific and efficient adhesion of targeted MBs to LNCaP cells. To our knowledge, this work reports the first model of polymeric MBs appropriately engineered to target PSMA, which might be further optimized and used for PCa diagnosis and potential carriers for selective drug delivery.

Design of Novel Bioisosteres of β-Diketo Acid Inhibitors of HIV-1 Integrase

HIV-1 integrase (IN) is an attractive and validated target for the development of novel therapeutics against AIDS. Significant efforts have been devoted to the identification of IN inhibitors using various methods. In this context, through virtual screening of the NCI database and structure-based drug design strategies, we identified several pharmacophoric fragments and incorporated them on various aromatic or heteroaromatic rings. In addition, we designed and synthesized a series of 5-aryl(heteroaryl)-isoxazole-3-carboxylic acids as biological isosteric analogues of β-diketo acid containing inhibitors of HIV-1 IN and their derivatives. Further computational docking studies were performed to investigate the mode of interactions of the most active ligands with the IN active site. Results suggested that some of the tested compounds could be considered as lead compounds and suitable for further optimization.

From Ligand to Complexes. Part 2. Remarks on Human Immunodeficiency Virus type 1 Integrase Inhibition by β-Diketo Acid Metal Complexes

Previously, we synthesized a series of beta-diketo acid metal complexes as novel HIV-1 integrase (IN) inhibitors (J. Med. Chem. 2006, 46, 4248-4260). Herein, a further extension of this study is reported. First, detailed docking studies were performed in order to investigate the mode of binding in the active site of the free ligands and of their metal complexes. Second, a series of potentiometric measurements were conducted for two diketo acids chosen as model ligands, with Mn(2+) and Ca(2+), in order to outline a speciation model. Third, we designed and synthesized a new set of complexes with different stoichiometries and tested them in an in vitro assay specific for IN. Finally, we obtained the first X-ray structure of a metal complex with HIV-1 IN inhibition activity. Analysis of these results supports the hypothesis that the diketo acids could act as complexes and form complexes with the metal ions on the active site of the enzyme.

Design and synthesis of novel dihydroquinoline-3-carboxylic acids as HIV-1 integrase inhibitors

Previously, we discovered linomide analogues as novel HIV-1 integrase (IN) inhibitors. Here, to make possible structure-activity relationships, we report on the design and synthesis of a series of substituted dihydroquinoline-3-carboxylic acids. The crystal structure of the representative compound 2c has also been solved. Among the eight new analogues, 2e showed a potency in inhibiting IN strand transfer catalytic activity similar to the reference diketo acid inhibitor L-731,988 (IC(50)=0.9 microM vs. 0.54 microM, for 2e and L-731,988, respectively). Furthermore, none of the compounds showed significant cytotoxicity in two tested cancer cell lines. These compounds represent an interesting prototype of IN inhibitors, potentially involved in a metal chelating mechanism, and further optimization is warranted.