Current Medicinal Chemistry - Volume 21, Issue 36, 2014

The blood-brain barrier (BBB), formed by brain capillary endothelial cells, prevents the entry of several drug molecules to the brain, especially molecules hydrophilic in nature. Advanced drug carriers like nanoparticles share the potential to allow entry of therapeutic proteins and genetic molecules into the central nervous system (CNS). Taking a targeting approach by conjugating molecules acting as ligands or monoclonal antibodies with affinity for proteins expressed on the luminal side of brain capillary endothelial cells, the nanoparticles can be designed to enable transport into the brain endothelium, or perhaps even through the endothelium leading to blood to brain transport. Currently, the iron-binding protein transferrin or antibodies raised against the transferrin receptor denote the most feasible molecule for targeting purposes at the BBB. This manuscript reviews the targetability of nanoparticles to the brain capillary endothelial cells, how nanocarriers may enter and transfer through the brain endothelium, and how likely restraints denoted by the threedimensional mesh of the extracellular proteins forming the brain capillary basement membrane challenge the possibilities for enabling transport of large molecules through the BBB encapsulated in nanoparticles.

Nanomedicine has recently emerged as an exciting tool able to improve the early diagnosis and treatment of a variety of intractable or age-related brain disorders. The most relevant properties of nanomaterials are that they can be engineered to cross the blood brain barrier, to target specific cells and molecules and to act as vehicles for drugs. Potentially beneficial properties of nanotherapeutics derived from its unique characteristics include improved efficacy, safety, sensitivity and personalization compared to conventional medicines. In this review, recent advances in available nanostructures and nanomaterials for brain applications will be described. Then, the latest applications of nanotechnology for the diagnosis and treatment of neurological disorders, in particular brain tumors and neurodegenerative diseases, will be reviewed. Recent investigations of the neurotoxicity of the nanomaterial both in vitro and in vivo will be summarized. Finally, the ongoing challenges that have to be meet if new nanomedical products are to be put on the market will be discussed and some future directions will be outlined.

Neuromedicine has recently been emerging on the research scene and presents interesting challenges in therapeutics. The range of therapies generally used to treat neurological disorders are limited in their efficacy and degree of patient compliance because of the necessity of multiple drug dosages, low drug concentration in the central nervous system and side effects. Moreover, therapeutics require standard drug dosages which cannot be personalized. The limiting obstacle in neuromedicine is still the blood-brain barrier, which prevents the accumulation of endogenous and exogenous compounds inside the brain. Various transporters located on the blood-brain barrier modulate the crossing of endogenous compounds. It has been discovered that these transporters can be used as pathways for the transport of therapeutic agents and macromolecules that pass the blood-brain barrier allowing the uptake of bioactive compounds into the central nervous system. Several attempts have recently been made to develop forms of nanomedicine capable of overcoming the limitations of conventional therapy, above all the crossing of the blood-brain barrier. An outstandingly promising option could be the use of colloidal supramolecular aggregates. These nanodrugs are safe, biodegradable, and biocompatible and can combine biomaterials useful for diagnostic and therapeutical applications. They can be modified using monoclonal antibodies, proteins, peptides and macromolecules, thus providing personalized neuromedicine, which can be used in the treatment of various neurological disorders. In this review, recent advancements of supramolecular colloidal devices as neuromedicines are discussed, with particular focus on the latest developments.

Human health is severely hampered by a majority of the neurological disorders such as the brain tumors, degenerative Alzheimer’s disease, Parkinson’s disease and those involving inflammatory component. Owing to the stringent protection offered by the blood brain barrier, conventional therapeutics gain limited access and therefore, are therapeutically suboptimal. Hence, research has now focused to develop the novel drug delivery systems with a prime motto of maintaining therapeutic drug levels inside the brain, avoiding non-specific tissue distribution. The introduction of nanotechnology has addressed few of these objectives and opened up new avenues for even more improvization. To some extent, nanodelivery systems were successful in crossing the blood brain barrier and accessing the remote areas of the brain. They also have shown tremendous potential in delivering the therapeutic and diagnostic aids following systemic administration. What revolutionised the nano applications is the development of “smart” nanosystems, whose surface is tailor made for the effective theranostic delivery. However, a detailed understanding of the long term nanoformulation toxicities, along with the neuropathology, is the critical future question to be addressed. In this review, a brief introduction of the prominent neurological disorders and detailed applications of nanotechnology are discussed.

Up to date, Alzheimer’s Disease (AD) is considered as an “urgency” for public health, since it represents one of the most dramatic causes of death in adults. The drugs currently used for AD are only symptomatic, thus not curing the pathology, but only trying to slow or delay the progression of the pathology. Moreover, there is a total lack of early identification, with only “probable’’ or ‘‘possible’’ diagnosis of AD patients. With this review, we aimed to individuate and to highlight the most promising approaches for AD therapy and diagnosis. In this view, at the cutting-edge of innovation, nanocarriers as polymeric nanoparticles, liposomes, nanoassembly and dendrimers, have been studied and investigated in order to ameliorate the detection (in vitro and in vivo) and/or the therapeutic options in AD. In this review, the most outstanding nanomedicine-driven approaches in AD imaging/detection and treatments are summarized in order to help in individuating values and criticisms. Moreover, an overview of one of the most innovative strategies in AD management, namely theranostic nanomedicine, is reported and commented.

Human immunodeficiency virus (HIV) infection commonly results in a myriad of comorbid conditions secondary to immune deficiency. Infection also affects broad organ system function. Although current antiretroviral therapy (ART) reduces disease morbidity and mortality through effective control of peripheral viral load, restricted infection in HIV reservoirs including gut, lymphoid and central nervous system tissues, is not eliminated. What underlies these events is, in part, poor ART penetrance into each organ across tissue barriers, viral mutation and the longevity of infected cells. We posit that one means to improve these disease outcomes is through nanotechnology. To this end, this review discusses a broad range of cutting-edge nanomedicines and nanomedicine platforms that are or can be used to improve ART delivery. Discussion points include how polymer-drug conjugates, dendrimers, micelles, liposomes, solid lipid nanoparticles and polymeric nanoparticles can be harnessed to best yield cell-based delivery systems. When completely developed, such nanomedicine platforms have the potential to clear reservoirs of viral infection.