Current Pharmaceutical Design - Volume 23, Issue 21, 2017

Background: Numerous theoretical studies have been performed to iteratively optimize the physicochemical properties such as dendrimer size and surface constituents in solution, as well as their molecular recognition properties for drugs, lipid membranes, nucleic acids and proteins, etc. Molecular modeling approaches such as docking and molecular dynamic (MD) simulations have supported experimental efforts by providing important insights into the structural properties of dendrimers in solution and possible binding properties of drugs at the atomic level. Method: We review the utilization of molecular modelling tools to obtain insight into the study and design of dendrimers, with particular importance placed on the improvement of binding properties of dendrimers for their use as drug nanocarriers and to increase the water solubility properties and drug delivery. Results: The modeling studies discussed in this review have provided substantial insight into the physicochemical properties of dendrimers in solution, including solvent pH and counterion distribution, at the atomic level, as well as the elucidation of some of the key interactions in solution of unmodified and modified dendrimers with some drugs of pharmaceutics interest and biological systems such as nucleic acids, proteins and lipid membranes. Conclusion: the described studies illustrate that whether simulations will be run at the all-atom or coarse-grained level, physicochemical conditions such as the type of force field, the treatment of electrostatics effects, counterion distribution, protonation state of dendrimers, and dendrimer concentrations which have been probed to play a crucial role in the structural behavior and binding properties must be prudently incorporated in the simulations.

Dendrimers are monodisperse, regular, three-dimensional and small-scale macromolecules that can be used to release substances such as drugs, markers, and genetic material into the cells. Among these substances, nucleic acids such as plasmid DNA, antisense oligonucleotides (asODN), and small-interfering RNA (siRNA) are widely used as therapeutic macromolecules for the treatment and prevention of diverse diseases. Several studies were focused on the modification of dendrimers aiming to improve their affinity for nucleic acids and their ability to release nucleic acids inside the cells. However, high-generation dendrimers have been shown to provoke leaking of cell membranes due to high surface-charge density. Thereby, despite the high potential of dendrimers, cytotoxicity still represents a problem to be solved prior to future in-vitro and in-vivo applications. Many approaches have proposed the introduction of diverse functional groups in low generation dendrimers, to reduce potential surface-charge density, without a loss in the ability to interact with nucleic acids. Another issue that should be addressed is how to modulate the affinity of dendrimers for nucleic acids at different pH values to guarantee an adequate release of the cargo in endosomal vesicles. These questions may be addressed through the aid of computational chemistry and bioinformatics tools. Therefore, the present review aims to provide a detailed review focused on the several techniques that have been developed for the study and design of dendrimers as carriers for DNA or RNA. Conclusions: As shown in the present review, molecular dynamics simulations can contribute by studying at theoretical level dendrimer-nucleic acid complexes at different conditions, such as pH or ionic strength. Therefore, different cell conditions such as the stay at the cytoplasm and the transit towards endosomes can be addressed. The influence of different terminal groups of dendrimers to DNA/RNA binding can also be evaluated using molecular simulations and especially, by using free energy methods, which aim to determine affinity of dendrimers for nucleic acids. The development of a library of terminal groups for dendrimers may represent a significant contribution to the design of new dendrimers. In this regard, protein-DNA interactions of structure databases have been analyzed as a way to identify suitable residues that can be incorporated as terminal groups of dendrimers. In summary, computational chemistry and biology tools will aim the design of new dendrimers for different kinds of cargo molecules.

Nanomedicine is the application of nanotechnology to medicine. This field is related to the study of nanodevices and nanomaterials applied to various medical uses, such as in improving the pharmacological properties of different molecules. Dendrimers are synthetic nanoparticles whose physicochemical properties vary according to their chemical structure. These molecules have been extensively investigated as drug nanocarriers to improve drug solubility and as sustained-release systems. New therapies such as gene therapy and the development of nanovaccines can be improved by the use of dendrimers. The biophysical and physicochemical characterization of nucleic acid/peptide-dendrimer complexes is crucial to identify their functional properties prior to biological evaluation. In that sense, it is necessary to first identify whether the peptide-dendrimer or nucleic aciddendrimer complexes can be formed and whether the complex can dissociate under the appropriate conditions at the target cells. In addition, biophysical and physicochemical characterization is required to determine how long the complexes remain stable, what proportion of peptide or nucleic acid is required to form the complex or saturate the dendrimer, and the size of the complex formed. In this review, we present the latest information on characterization systems for dendrimer-nucleic acid, dendrimer-peptide and dendrimer-drug complexes with several biotechnological and pharmacological applications.

Background: Disseminated metastatic cancer requires insistent management owing to its reduced responsiveness for chemotherapeutic agents, toxicity to normal cells consequently lower survival rate and hampered quality of life of patients. Methods: Dendrimer mediated cancer therapy is advantageous over conventional chemotherapy, radiotherapy and surgical resection due to reduced systemic toxicity, and molecular level cell injury to cancerous mass, for an appreciable survival of the subject. Recently used dendrimer mediated nanotechnology for oncology aims to conquer these challenges. Dendrimers based nano-constructs are having architectures comparable to that of biological vesicles present in the human body. Results: Operating with dendrimer technology, proffers the exclusive and novel strategies with numerous applications in cancer management involving diagnostics, therapeutics, imaging, and prognostics by sub-molecular interactions. Dendrimers are designed to acquire the benefits of the malignant tumor morphology and characteristics, i.e. leaky vasculature of tumor, expression of specific cell surface antigen, and rapid proliferation. Conclusion: Dendrimers mediated targeted therapy recommends innovatory function equally in diagnostics (imaging, immune-detection) as well as chemotherapy. Currently, dendrimers as nanomedicine has offered a strong assurance and advancement in drastically varying approaches towards cancer imaging and treatment. The present review discusses different approaches for cancer diagnosis and treatment such as, targeted and control therapy, photodynamic therapy, photo-thermal therapy, gene therapy, antiangiogenics therapy, radiotherapy etc.

Ovarian cancer, the worldwide leading cause of gynecological cancer-related death, is primarily treated by surgery followed by platinum chemotherapy. Though the tumor initially responds to the treatment, only 30% of 5 year survival period has been recorded and this is mainly attributed to the acquired chemo resistance and frequent recurrence of tumor. Combination chemotherapy as well, led to therapeutic failure due to non-specificity and subsequent side effects. However, polymer mediated drug delivery aids in overcoming these impediments. In particular, three dimensional macromolecule “Dendrimer” with its unique properties and numerous functionalities offer various advantages over the conventional approach and may improve the treatment outcome in patients with ovarian cancer. The present review highlights the various strategies employed using dendrimers to achieve targeted drug delivery and enhanced therapeutic efficacy in ovarian cancer.

Background: The brain is a well-protected organ, with a complex system of cells, proteins and transporters, that acts as a sentinel to prevent potentially harmful substances from entering the brain, stopping also active molecules administered with a therapeutic goal. Although their limited exploitation, dendrimers are currently under evaluation as drug vectors to improve pharmacological treatments, targeting active molecules across the blood-brain barrier and penetrating brain tissues. Methods: Up to date, only three different families of dendrimers, poly(amidoamine)-, poly(propyleneimine)- and poly(L-lysine)-based, have found application as drug transporters in the Central Nervous System. Their development, functionalization and characterization are reported in the literature, with interesting preliminary outcomes in the treatment of brain disorders. Surface functionalization also affects the interaction between dendrimers and cells or tissues, with effects not only on penetration and retention, but also on the safety profile of this drug carrier. Conclusion: This review focuses on the application of dendrimers in the field of targeted drug delivery toward the Central Nervous System, highlighting their interesting properties. Discussion will be promising and represent an important starting point for a further diffusion of dendrimers in pharmacological treatment of the Central Nervous System.

Background: Lipid nanoparticles have been studied mainly as a means of transporting and releasing drugs. A special emphasis has been placed on designing nanoparticles that improve the delivery of drugs with targets in the central nervous system. Methods: The biomedical literature was searched for basic and clinical studies. The recent applications are described and related with their bioactivities. Results: The current review compiles data on the components and features of lipid nanoparticle systems as well as the necessary conditions for their selective action. As an example of their application, we present data from preclinical and clinical studies on lipid nanoparticles used as potent and efficient agents in the diagnosis and treatment of some neurodegenerative maladies, including Parkinson's disease. Conclusion: Current evidence supports the application of lipid nanoparticles for designing drugs carriers for neurodegenerative diseases. Also, we have gathered data that suggests a role of drug-free lipid nanoparticles as neuroprotective or preventive agents during neurodegenerative processes.

Background: Dendrimers are hyperbranched polymeric nanomaterials increasingly used in research, industrial and biomedical applications. Establishing safety profile of these particles includes an understanding of their interactions with blood components and the immune system. Method: Herein I review the literature demonstrating how tuning dendrimer physicochemical properties influences their interaction with erythrocytes, platelets, plasma proteins, complement and coagulation systems. Dendrimer immunogenicity, adjuvanticity, allergenicity, anti-inflammatory, immunosuppressive and antibacterial properties are also discussed. Conclusion: Dendrimers hemato- and immune- compatibility are determined by particle size, architecture, type and density of surface functional groups. Case studies from the literature are discussed to support this conclusion. The review also highlights questions which require more thorough investigation to fill the gaps in our understanding of immunological properties of dendrimers.

Background: Dendrimers and hyperbranched polymers are emerging polymer architectures that attract increasing attention due to their unique topological structure and interesting physicochemical properties. Their enormous potential makes them particularly attractive to form new and fascinating nanometric drug delivery systems, solving several typical shortcomings encountered in nanomedicine. Objective: In this context, the recent developments of dendritic and hyperbranched based systems, together with their application as nanocarriers, have been comprehensively reviewed. Conclusion: This review highlights how the structural complexity can be taken as an evolution parameter of these nanosystems, starting with hyperbranched polymers and evolving to more complex structures such as hybrid dendritic-inorganic nanoparticles and dendronized nano-objects hierarchically designed. Finally, future directions and perspectives in this promising field are briefly discussed.

Background: Mood disorders, consisting of unipolar and bipolar depression, are complex diseases characterized by depressed mood and anhedonia. These core symptoms are accompanied in a varying manner by anxiety, several neurovegetative symptoms and cognitive impairment. Mood disorders are characterized by decreases in neurogenesis, alteration in synaptic structure and synaptic transmission, all of them regulated by BDNF, a neurotrophin that performs multiple functions in the adult central nervous system. Many evidences show that BDNF is critically decreased in mood disorders and plays an essential role in most anti-depressant treatments. In turn, the transcription factor NF-kB has recently emerged as an important player in the pathophysiology of depression, with roles in neurogenesis, synaptic transmission and plasticity. Methodology: We review the bidirectional interactions between BDNF and NF-kB signaling pathways. Results and Conclusions: We discuss a potential beneficial effect of a positive feedback loop between BDNF and NF-kB activated pathways in antidepressant action. This could be transduced into the identification of downstream NF-kB gene targets able to potentiate antidepressant mechanisms, thus guiding the development of novel and faster acting antidepressant drugs.

Exploring a new target for antibacterial drug discovery has gained much attention because of the emergence of Multidrug Resistance (MDR) strains of bacteria. To overcome this problem the development of novel antibacterial was considered as highest priority task and was one of the biggest challenge since multiple factors were involved. The bacterial peptidoglycan biosynthetic pathway has been well documented in the last few years and has been found to be imperative source for the development of novel antibacterial agents with high target specificity as they are essential for bacterial survival and have no homologs in humans. We have therefore reviewed the process of peptidoglycan biosynthesis which involves various steps like formation of UDP-Nacetylglucosamine (GlcNAc), UDP-N-acetylmuramic acid (MurNAc) and lipid intermediates (Lipid I and Lipid II) which are controlled by various enzymes like GlmS, GlmM, GlmU enzyme, followed by Mur Ligases (MurAMurF) and finally by MraY and MurG respectively. These four amide ligases MurC-MurF can be used as the source for the development of novel multi-target antibacterial agents as they shared and conserved amino acid regions, catalytic mechanisms and structural features. This review begins with the need for novel antibacterial agents and challenges in their development even after the development of bacterial genomic studies. An overview of the peptidoglycan monomer formation, as a source of disparity in this process is presented, followed by detailed discussion of structural and functional aspects of all Mur enzymes and different chemical classes of their inhibitors along with their SAR studies and inhibitory potential. This review finally emphasizes on different patents and novel Mur inhibitors in the development phase.