ABSTRACT For Magnetic Resonance Imaging (MRI) visualization of molecular markers —β-amyloid peptide (βA)— of Alzheimer's disease, the use of contrast agents (CAs) is necessary. In clinical practice, obtaining gadolinium(III) oxide nanoparticles (Gd2O3NPs) as ACs is a very active field of research. In this work, one of the Amylovis® compounds, naphthalene derivatives obtained at CNEURO with high affinity for βA, was conjugated to Gd2O3NPs. The Gd2O3NPs were characterized by FT-IR, TEM, TGA, DLS and ζ-potential. By FT-IR and TEM, respectively, the functionalization with carboxyl groups and the size of the Gd2O3NPs (< 10 nm) were corroborated. Although the amount of Amylovis®-204 conjugated could decrease the colloidal stability of Gd2O3NPs, the values of hydrodynamic diameters (< 200 nm) and longitudinal relaxivity of Gd2O3NPs justify their potential use as AC for the proposed purpose.

RESUMEN Para la visualización por Resonancia Magnética de Imágenes (RMI) de los marcadores moleculares —péptido β-amiloide (βA)— de la enfermedad de Alzheimer, es necesario el empleo de agentes de contrastes (ACs). En la práctica clínica, la obtención de nanopartículas de óxido de gadolinio(III) (Gd2O3NPs) como ACs es un campo de investigación muy activo. En este trabajo se conjugó a Gd2O3NPs uno de los compuestos Amylovis®, derivados del naftaleno, obtenidos en CNEURO, con gran afinidad por el βA. Las Gd2O3NPs se caracterizaron por FT-IR, TEM, TGA, DLS y Potencial ζ. Por FT-IR y TEM, respectivamente. Se corroboró la funcionalización con grupos carboxilos y el tamaño de las Gd2O3NPs (< 10 nm). Si bien la cantidad de Amylovis®-204 que se conjuga pude disminuir la estabilidad coloidal de las Gd2O3NPs, los valores de diámetros hidrodinámicos (< 200 nm) y relaxitividad longitudinal de las Gd2O3NPs, justifican su empleo potencial como AC para el fin propuesto.

ABSTRACT Magnetic iron oxide nanoparticles (NPs) have been widely used as contrast agents in magnetic resonance imaging. In recent years, interest has been focused on obtaining and functionalizing them to make them better vectors and more soluble or specific to a given target. In the present work, we report the synthesis and characterization of NPs functionalized with two naphthalene derivatives (Amylovis(), which exhibit high affinity for β-amyloid plaques characteristic of Alzheimer's disease (AD). These ones were characterized by FT-IR, TGA, DLS and SEM. The obtained NPs were conjugated by Steglich's method to two different Amylovis( molecules, determined this by ligand differences on the surface of the synthesized NPs. Amylovis( functionalized NPs could be useful for the detection of amyloid plaques that would contribute to an early diagnosis of AD.

RESUMEN Las nanopartículas (NPs) magnéticas de óxido de hierro se han utilizado ampliamente como agentes de contraste en resonancia magnética de imágenes. En los últimos años, el interés se ha enfocado a su obtención y funcionalización para que sean mejores vectores y más solubles o específicas a un blanco determinado. En el presente trabajo se reporta la síntesis y caracterización de NPs de óxido de hierro funcionalizadas con dos derivados de naftaleno, que exhiben una alta afinidad por las placas de β-amiloide. Las mismas se caracterizaron por FT-IR, TGA, DLS y SEM. Las NPs obtenidas se conjugaron por el método de Steglich a dos moléculas de Amylovis( diferentes, determinado esto por las diferencias de ligando en la superficie de las NPs sintetizadas. Las NPs funcionalizadas con Amylovis( podrían ser útiles para la detección de placas ( amiloides que contribuirían a un diagnóstico precoz de la enfermedad de Alzheimer.

ABSTRACT Specific contrast agents facilitate the use of Magnetic Resonance Imaging (MRI) in the early diagnosis of Alzheimer's disease (AD). In the present work, a procedure for the synthesis of a potential MRI contrast agent based on PEGylated Gd2O3 particles is developed for conjugation to Amylovis®, a family of compounds that has shown a high affinity for the pathological structures present in AD. The products obtained were characterized by FT-IR, ICP, TGA, DLS and SEM. Amylovis-functionalized Gd2O3 particles showed a spherical morphology, with an average hydrodynamic diameter of 2.5 μm. These particles presented an adequate value of the ratio between the longitudinal (r1) and transversal (r2) relaxivities (r2/r1 = 2.4). This suggests that once these particles have a hydrodynamic diameter smaller than 200 nm, they could be used as a potential contrast agent for MRI.

RESUMEN Los agentes de contrastes específicos facilitan el empleo de la Resonancia Magnética de Imágenes (RMI) en el diagnóstico precoz de la enfermedad de Alzheimer (EA). En el presente trabajo se desarrolla un procedimiento de síntesis de un potencial agente de contraste para IRM basado en partículas de Gd2O3 pegiladas para conjugarlas a Amylovis®, familia de compuestos que ha mostrado una alta afinidad por las estructuras patológicas presentes en la EA. Los productos obtenidos se caracterizaron por FT-IR, ICP, TGA, DLS y SEM. Las partículas de Gd2O3 funcionalizadas con Amylovis mostraron una morfología esférica, con un diámetro hidrodinámico promedio de 2,5 μm. Dichas partículas presentaron un adecuado valor de la relación entre las relaxitividades longitudinal (r1) y transversal (r2) (r2/r1 = 2.4). Lo anterior sugiere que una vez logrado que dichas partículas presenten un diámetro hidrodinámico menor que 200 nm, pudieran ser empleadas como un potencial agente de contraste para IRM.

Alzheimer´s disease (AD) is characterized by a progressive loss of cognitive functions and the present of ß -amyloid plaques in the cerebral cortex. Magnetic resonance imaging (MRI) is the most used technique for diagnostic of AD. The amyloid and metal hypothesis have opened an important field of research in the Inorganic Chemistry discipline in the search for contracting agents (based on paramagnetic metal ions), radiopharmaceuticals taking into account the possibility of labeling of some metal ions and complexes with ionic metals which are kinetic inert that inhibit the aggregation of ß -amyloid plaques by various mechanisms. In the present paper we report the importance of the early diagnosis of AD, the imaging techniques used in its detection and the metal compounds involved in the search for a safe early diagnosis and effective therapy.

La enfermedad de Alzheimer (EA) se caracteriza por la pérdida progresiva de las funciones cognitivas y la presencia en el cerebro de placas ß-amiloide. La Resonancia Magnética de Imágenes (RMI) es la técnica de imagen más utilizada en el diagnóstico de Alzheimer. La hipótesis amiloide y la metálica han abierto un importante campo de investigación en la disciplina Química Inorgánica, en la búsqueda de agentes de contrates basados en iones metálicos paramagnéticos, de radiofármacos, teniendo en cuenta la posibilidad de marcajes de algunos iones metálicos y de complejos con iones metálicos cinéticamente inertes que inhiben la agregación de las placas ß-amiloides por diversos mecanismos. En el presente trabajo se reporta la importancia del diagnóstico precoz de la EA, las técnicas de imágenes más utilizadas en su detección y los compuestos metálicos involucrados en la búsqueda de un diagnóstico precoz certero y una terapia eficaz.

ABSTRACT INTRODUCTION Alzheimer disease is the main cause of dementia associated with aging in Cuba and the world. Development of methods for early diagnosis is vital to increasing intervention effectiveness and improving patient quality of life. Recent studies have shown associations between alterations in serum levels of antineuronal antibodies and Alzheimer disease pathology. However, the specific relationship between such antineuronal antibodies and Alzheimer pathogenesis remains unclear because of the great variety of antibodies identified and their heterogeneity among patients and nondemented controls. OBJECTIVE Assess the association between serum levels of antibodies against neuronal antigens (total brain protein, aldolase and amyloid beta protein) and cognitive performance in older Cuban adults. METHODS A cross-sectional pilot study was conducted of adults aged ≥65 years living in Havana’s Playa Municipality and Artemisa Province (southwest of Havana). A sociodemographic and risk factor questionnaire was administered, neuropsychological assessment conducted, and physical and neurological examinations performed. A relative or caregiver was also interviewed. Laboratory tests included: complete blood count, glycemia, lipid panel, and apolipoprotein E genotype. Of 143 individuals studied, 33 were cognitively normal, 52 had mild cognitive impairment, and 58, probable Alzheimer disease. Serum antibody levels were determined by ELISA and compared using covariance analysis with a significance level of 0.05. ELISA specificity, sensitivity and predictive value were assessed by analyzing their respective diagnostic performance curves. RESULTS Patients with probable Alzheimer disease performed least well on the mini mental state examination (cognitively normal 28.8, SD 1.2; mild cognitive impairment 27.4, SD 2.2; probable Alzheimer disease 12.9, SD 6.5; ANOVA p <0.001). The percentage of Apo E4 carriers was seven times greater in the group with probable Alzheimer disease than in the cognitively normal group. Among the antibodies studied, only those against amyloid beta peptide had levels significantly higher in the Alzheimer disease group than in the cognitively normal group (p = 0.007) and the group with mild cognitive impairment (p = 0.002). CONCLUSIONS Results support the presence of an autoimmune component in Alzheimer disease and suggest that serum anti–amyloid-beta could be used for its diagnosis.