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The majority of heterocycle compounds and typically common heterocycle fragments present in most pharmaceuticals currently marketed, alongside with their intrinsic versatility and unique physicochemical properties, have poised them as true cornerstones of medicinal chemistry. Apart from the already marketed drugs, there are many other being investigated for their promising activity against several malignancies. In particular, anticancer research has been capitalizing on the intrinsic versatility and dynamic core scaffold of these compounds. Nevertheless, as for any other promising anticancer drugs, heterocyclic compounds do not come without shortcomings. In this review, we provide for a concise overview of heterocyclic active compounds and families and their main applications in medicine. We shall focus on those suitable for cancer therapy while simultaneously addressing main biochemical modes of action, biological targets, structure-activity relationships as well as intrinsic limitation issues in the use of these compounds. Finally, considering the advent of nanotechnology for effective selective targeting of drugs, we shall discuss fundamental aspects and considerations on nanovectorization of such compounds that may improve pharmacokinetic/pharmacodynamic properties of heterocycles.

Traditional methods of drug delivery present several drawbacks, mainly due to off-target effects that may originate severe side and toxic effect to healthy tissues. Parallel to the development of novel more effective drugs, particular effort has been dedicated to develop and optimize drug delivery vehicles capable of specifically targeting the required tissue/organ and to deliver the cargo only where and when it is needed. New drug delivery systems based on nanoscale devices showing new and improved pharmacokinetic and pharmacodynamics properties like enhanced bioavailability, high drug loading or systemic stability have surged in the past decade as promising solutions to the required therapeutic efficacy. Amongst these nanoscale vectors, nanoparticles for drug delivery, such as polymeric, lipidbased, ceramic or metallic nanoparticles, have been at the forefront of pharmaceutical development. The interest in nanomedicine for treatment and diagnosis is clearly reflected on the increasing number of publications and issued patents every year. Here, we provide a broad overview of novel nanoparticle based drug delivery systems, ranging from polymeric systems to metal nanoparticles, while simultaneously listing the most relevant related patents.

Over the past few years, modern medicinal chemistry has evolved towards providing us new and alternative chemotherapeutic compounds with high cytotoxicity towards tumor cells, alongside with reduced side effects in cancer patients. Organometallic compounds and their unique physic-chemical properties typically used in homogenous catalysis are now being translated as potential candidates for medical purposes. Their structural diversity, ligand exchange, redox and catalytic properties make them promising drug candidates for cancer therapy. Over the last decade this area has witnessed a steady growth and a few organometallic compounds have in fact already entered clinical trials, emphasizing its increasing importance and clinical relevance. Here we intend to stress out the different applications of organometallic compounds in medicine with emphasis on cancer therapy, as well as address setbacks regarding formulation issues, systemic toxicity and off-target effects. Advantages over classical coordination metal complexes, their nanovectorisation and specific molecular targets are also discussed.

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Mesenchymal stem cells are multipotent adult stem cells capable of generating bone, cartilage and fat, and are thus currently being exploited for regenerative medicine. When considering osteogenesis, developments have been made with regards to chemical induction (e.g. differentiation media) and physical induction (e.g. material stiffness, nanotopography), targeting established early transcription factors or regulators such as runx2 or bone morphogenic proteins and promoting increased numbers of cells committing to osteo-specific differentiation. Recent research highlighted the involvement of microRNAs in lineage commitment and terminal differentiation. Herein, gold nanoparticles that confer stability to short single stranded RNAs were used to deliver MiR-31 antagomiRs to both pre-osteoblastic cells and primary human MSCs in vitro. Results showed that blocking miR-31 led to an increase in osterix protein in both cell types at day 7, with an increase in osteocalcin at day 21, suggesting MSC osteogenesis. In addition, it was noted that antagomiR sequence direction was important, with the 5 prime reading direction proving more effective than the 3 prime. This study highlights the potential that miRNA antagomiR-tagged nanoparticles offer as novel therapeutics in regenerative medicine.

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The therapeutic promise of small interfering RNAs (siRNAs) for specific gene silencing is dependent on the
successful delivery of functional siRNAs to the cell cytoplasm. Their conjugation to an established delivery
platform, such as gold nanoparticles, offers a huge potential for treating diseases and advancing our
understanding of cellular processes. The success or failure is dependent on both the uptake of the nanoparticlesinto the cells and subsequent intracellular release of the functional siRNA. In this paper, utilising gold nanoparticle siRNA-mediated delivery against C-MYC, we aimed to determine if we could achieve knockdown in a cancer cell line with low levels of intracellular glutathione, and determine the influence, if any, of polyethylene glycol (PEG) ligand density on knockdown, with a view to determine the optimal nanoparticle
design to achieve C-MYC knockdown. We demonstrate that, regardless of the PEG density, knockdown in cells with relatively low glutathione levels can be achieved, and also the possible effect of steric hindrance in terms of PEG on the availability of the siRNA for cleavage in the intracellular environment. Gold nanoparticle uptake was demonstrated via transmission electron microscopy and mass spectroscopy, whilst knockdown was determined at the protein and physiological levels (cells in S-phase) by in-cell westerns and BrdU incorporation, respectively.

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Gene therapy arises as a great promise for cancer therapeutics due to its potential to silence genes involved in tumor development. In fact, there are some pivotal gene drivers that suffer critical alterations leading to cell transformation and ultimately to tumor growth. In this vein, gene silencing has been proposed as an active tool to selectively silence these molecular triggers of cancer, thus improving treatment. However, naked nucleic acid (DNA/RNA) sequences are reported to have a short lifetime in the body, promptly degraded by circulating enzymes, which in turn speed up elimination and decrease the therapeutic potential of these drugs. The use of nanoparticles for the effective delivery of these silencers to the specific target locations has allowed researchers to overcome this issue. Particularly, gold nanoparticles (AuNPs) have been used as attractive vehicles for the target-specific delivery of gene-silencing moieties, alone or in combination with other drugs. We shall discuss current trends in AuNP-based delivery of gene-silencing tools, considering the promising road ahead without overlooking existing concerns for their translation to clinics

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Several copper complexes have been assessed as anti-tumor agents against cancer cells. In this work, a copper compound [Cu(H2O){OS(CH3)2}L](NO3)2 incorporating the ligand 4'-phenyl-terpyridine antiproliferative activity against human colorectal, hepatocellular carcinomas and breast adenocarcinoma cell lines was determined, demonstrating high cytotoxicity. The compound is able to induce apoptosis and a slight delay in cancer cell cycle progression, probably by its interaction with DNA and induction of double-strand pDNA cleavage, which is enhanced by oxidative mechanisms. Moreover, proteomic studies indicate that the compound induces alterations in proteins involved in cytoskeleton maintenance, cell cycle progression and apoptosis, corroborating its antiproliferative potential.