"The work of this thesis is based on research on peptides able to cross the blood-brain barrier and their use as tools to enable the delivery of drugs into the brain. The blood-brain barrier (BBB) is a permeable but selective barrier that tightly regulates the transport into the central nervous system (CNS). In this regard, therapeutic treatments at the CNS are hampered by the presence of this barrier (BBB). Thus, diverse strategies have been developed to overcome it. Blood-brain barrier shuttles are peptides able to cross this barrier and deliver drugs into the brain. Peptides are privileged structures from the therapeutic point of view, they share properties from small organic molecules and large biologics: the synthesis through solid-phase peptide synthesis (SPPS) enables a straightforward method to obtain them with high purity and at the same time they can be purified and characterized like small organic compound. In addition, their structure is present in nature and thus the risk of toxicity is lower or more predictable compared with organic compounds, and their larger structure enables to obtain more selective and stronger interactions with targets. In addition, peptides have been shown to cross the BBB by diverse transport mechanisms and thus enabling to select the best one for each therapy and drug. In this thesis a family of BBB shuttles crossing by passive diffusion (based on phenylproline) have been improved from a parent peptide shuttle (based on N-methyl-phenylalanine). The solubility was three orders of magnitude superior and the transport capacity was maintained upon cargo attachment. In addition, the role of stereochemistry in passive diffusion in biological membranes was demonstrated. A method which combined the use of MALDI-TOF MS and in vitro cell-based models of the BBB enabled the increase in sensitivity for transport quantification of three orders of magnitude compared to RP-HPLC-PDA. Additionally, a BBB shuttle library was evaluated and quantified by this novel methodology. Two new analogs showed better performance when evaluated in these in vitro cell-based models. Immunogenicity of BBB shuttle peptides made by L- or D-amino acids was evaluated and compared. Both peptide shuttles showed low immunogenic response in mice, however, the response to those made with D- amino acids was lower. Finally, the applicability of these peptide shuttles for a therapeutic use was considered for Friedreich's Ataxia, a monogenic recessive disease. Both a protein replacement therapy and a gene therapy for the central nervous system were attempted by coupling covalently BBB shuttles to the affected protein or viruses, respectively. The protein replacement therapy was impeded by the high rate of proteolysis of the protein used. On the other hand, novel methods of conjugation of BBB shuttles into enveloped viruses (Herpes simplex Virus type 1; HSV- 1) were developed. These modified viral particles were subsequently characterized through a range of methods comprising molecular biology tools (SDS-PAGE, western blots), proteomics (mass spectrometry) and biophysical tools (dynamic light scattering and z-potential)". -- TDX.

La major part de fàrmacs dissenyats per tractar malalties del sistema nerviós central no són efectius perquè no poden creuar la barrera hematoencefàlica (BHE). Una de les estratègies més prometedores per superar aquest obstacle és l'ús de llançadores peptídiques. Tanmateix, l'eficiència i selectivitat d'aquests encara s'ha de millorar. Els objectius principals de la tesi eren, per una banda, trobar noves llançadores resistents a proteases i, per l'altra, augmentar el transport d'anticossos monoclonals a través de la BHE. Tenint en compte que l'apamina és un pèptid del verí de l'abella que creua la BHE, vam iniciar l'estudi demostrant que els residus implicats en la toxicitat no eren necessaris pel transport. Aleshores vam generar anàlegs simplificats i MiniAp-4 va mostrar el millor compromís entre estabilitat en sèrum, permeabilitat i immunogenicitat. Aquest pèptid va incrementar el transport de la GFP, quantum dots i nanopartícules d'or en un model cel·lular humà de BHE. A més, va augmentar en 7,6 vegades la concentració de cianina-5.5 en el cervell de ratolins. Pel que fa el transport d'anticossos, vam posar a punt diversos mètodes per conjugar els pèptids llançadora a diferents parts de la immunoglobulina, incloent els extrems Nterminals, les cadenes glicosídiques, les lisines i les cisteïnes. Cap conjugació va disminuir l'afinitat dels anticossos pels seus epítops exceptuant la del N-terminal. Vam escollir la modificació de les cisteïnes utilitzant química tiol-maleimida i també la de les lisines mitjançant cicloaddició alquí-azida catalitzada per coure (Cu15C) per generar conjugats emprant diverses llançadores. Alguns d'aquests van mostrar un transport significativament més elevat que l'anticòs sol en el model cel·lular humà de BHE, en especial una mini-apamina i el RVG29 enllaçats mitjançant Cu15C. La major eficiència de les llançadores amb aquesta unió és atribuïble a la major accessibilitat per interaccionar amb els seus receptors. Per concloure, en aquesta tesi hem generat anàlegs d'apamina resistents a protaeses, més reduïts, menys tòxics i menys immunogènics. A més, MiniAp-4 és capaç de transportar diversos compostos a través de la BHE in vitro i in vivo. També hem demostrat que el transport d'anticossos es pot augmentar mitjançant diferents llançadores peptídiques, incloent les mini-apamines.

The availability of various in vitro and in vivo techniques has considerably advanced the research on drug transport and metabolism across the blood-brain barrier (BBB). These specialized and sophisticated experimental strategies are of fundamental importance if one is to gain a greater understanding of enhanced and selective drug delivery to the brain. The reader will find in this book methods for in vitro endothelial/astrocyte cell culture models, and for in vivo intracerebral microdialysis to study drug tranport across the BBB. This book, however, is not merely a laboratory manual consisting of recipes for BBB research; it permits the presentation of the different methods in fine detail, revealing tricks and short cuts that frequently do not appear in the literature. The researcher is well aware that differences (subtle or otherwise) in experimental steps used in different laboratories may influence the outcome of any particular procedure. The book also illustrates the accessibility and the application of the different methods in different species. Background information of the protocol is given in every chapter, which also contains a literature list that the reader may wish to refer to for further information. This volume will be invaluable to basic researchers as well as to those involved in the search for agents suitable for pharmaceutic intervention in the central nervous system.

Brain Targeted Drug Delivery Systems: A Focus on Nanotechnology and Nanoparticulates provides a guide on nanoparticulates to both academic and industry researchers. The book discusses key points in the development of brain targeted drug delivery, summarizes available strategies, and considers the main problems and pitfalls evidenced in current studies on brain targeted drug delivery systems. As the brain is the most important organ in the human body, and disorders of the central nervous system (CNS) are the most serious threat to human life, this book highlights advances and new research in drug delivery methods to the brain. - Provides an overview of brain targeting drug delivery that is useful to both academic and industry-based researchers - Discusses key points in developing brain targeting drug delivery systems - Summarizes and presents currently available strategies for brain targeting drug delivery - Covers not only current studies and their strengths, but also gives insight into the pitfalls of current research