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This paper provides a mini-review of some recent approaches for the treatment of brain pathologies examining both medicinal chemistry and pharmaceutical technology contributions. Medicinal chemistry-based strategies are essentially aimed at the chemical modification of low molecular weight drugs in order to increase their lipophilicity or the design of appropriate prodrugs, although this review will focus primarily on the use of prodrugs and not analog development. Recently, interest has been focused on the design and evaluation of prodrugs that are capable of exploiting one or more of the various endogenous transport systems at the level of the blood brain barrier (BBB). The technological strategies are essentially non-invasive methods of drug delivery to malignancies of the central nervous system (CNS) and are based on the use of nanosystems (colloidal carriers) such as liposomes, polymeric nanoparticles, solid lipid nanoparticles, polymeric micelles and dendrimers. The biodistribution of these nanocarriers can be manipulated by modifying their surface physico-chemical properties or by coating them with surfactants and polyethylene-glycols (PEGs). Liposomes, surfactant coated polymeric nanoparticles, and solid lipid nanoparticles are promising systems for delivery of drugs to tumors of the CNS. This mini-review discusses issues concerning the scope and limitations of both the medicinal chemistry and technological approaches. Based on the current findings, it can be concluded that crossing of the BBB and drug delivery to CNS is extremely complex and requires a multidisciplinary approach such as a close collaboration and common efforts among researchers of several scientific areas, particularly medicinal chemists, biologists and pharmaceutical technologists.

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Translocator protein 18 kDa (TSPO) is a promising target for molecular imaging and for targeted drug delivery to tumors overexpressing TSPO. In our previous work, new macromolecular conjugates with a high affinity and selectivity for TSPO were prepared by conjugating the biodegradable poly(d,l-lactic-co-glycolic acid) (PLGA) polymer with two potent and selective TSPO ligands, namely, compounds 1 and 2. Based on this, nanoparticle delivery systems (NPs), employing TSPO ligand-PLGA conjugated (PLGA-TSPO) polymers, were prepared. Furthermore, to evaluate the ability of the new NPs to be used as a drug delivery systems for anticancer therapy, PLGA-TSPO NPs were loaded with 5-fluorouracil (5-FU), chosen as a model hydrophilic anticancer drug. The main goal of this work was to investigate the synergistic potential of using NP conjugates PLGA-TSPO, TSPO ligands being pro-apoptotic agents, to simultaneously deliver a cytotoxic anticancer drug. To better highlight the occurrence of synergistic effects, dual drug loaded PLGA NPs (PLGA NPs/5-FU/1) and dual drug loaded PLGA-TSPO NPs (PLGA-TSPO NPs/5-FU/1), with 5-FU and TSPO ligand 1 physically incorporated together, were also prepared and characterized. The particle size and size distribution, surface morphology, and drug encapsulation efficiency, as well as the drug release kinetics, were investigated. In vitro cytotoxicity studies were carried out on C6 glioma cells overexpressing TSPO, and to evaluate the potential uptake of these nanoparticulate systems, the internalization of fluorescent labeled PLGA-TSPO NPs (FITC-PLGA-TSPO NPs) was also investigated by fluorescence microscopy. Results demonstrated that PLGA-TSPO NPs/5-FU and dual drug loaded PLGA NPs/5-FU/1 and PLGA-TSPO NPs/5-FU/1 could significantly enhance toxicity against human cancer cells due to the synergistic effect of the TSPO ligand 1 with the anticancer drug 5-FU.