Medical and health sciences & Chemical sciences
University of Havana
Aramis Rivera was born on September 18, 1968, to a modest home of peasants. In 1998, she receiving her Msc. in Pharmaceutical Science in University of Havana and then her PhD in 2003.
Based on her Pharmaceutical and Materials Science backgrounds, the candidate has devoted her nearly 20-year career to put into practice medical applications of natural zeolites, and to study the potential for pharmaceufical applisatiens of microporoas and nanoporous materials in general. Her main basic contributions to these areas can be written as follows:
1) Contribution to the development of two new drugs based on zeolite - Neutacid (trademark) antacid tablets and Enterex- anti-diarrheic tablets. Neutacid; based on the neutralizing capacity of the purified natural clinoptilolite (NZ) from the Tasajeras deposit, Cuba, and is used for therapy in patients suffering from hyperacidity produced by gastric dyspepsia and gastric-duodenal ulcer. The excess of HCI in gastric juice is neutralized by NZ preserving the structural stability of pepsin. A pharmaceutical study conducted in Wistar rats has confirmed the neutralizting effect of the natural product. The same was observed when Neutacid tablets were contacted with gastric juice from patients suffering of hyperacidity. Three clinical tests showed the positive effect of the Neutacid chewing tablets therapy in patients suffering from hyperacidity. The patients did not refer such side effects as acid rebound or constipation because the structure of pepsin in the gastric juice remained stable. The physical and chemical properties of the antacid tablets remained stable after three year of storage at room conditions. Enterex: based on the bile acids, aflatoxine B1 and glucose adsorption capacity of NZ. It prevents, or at least controls diarrhea. In September 1995, the Cuban Drug Qualify Control Agency approved Enterex as a new drug, and the medical register was obtained (No. 0823).
2) Development of a new zeolite-based active principle antacid properties (NZ*). A new zeolitic active principle called NZ* with antacid properties was obtained. The-new product is the result of hydrothermal transformations applied to purified natural clinoptilolite. NZ* and other related products have been characterized physically and chemically. It was demonstrated that the structure of the zeolitic raw mineral remained unchanged after hydrothermal transformation, and that NZ* is structurally stable after interaction with synthetic gastric juice. The effect of NZ* dose on the gastric enzyme pepsin was also evaluated. It was demonstrated that the zeolitic active principles did not affect the concentration and stability of the enzyme pepsin in synthetic gastric juice.
3) Development of a zeolite-based antacid-aspirine composite. The use of pharmaceutical forms consisting in a combination of an antacid and aspirin (ASA) has been common practice in the pharmaceutical industry. Taking into account the antacid properties of NZ and its modified forms, the effects of them on ASA in an aqueous medium was explored. Additionally, interaction studies between these zeolitic materials and two drugs, metronidazole and sulfarnethoxazole, which cause considerable gastric side effects, were also conducted. The results indicated that both, zeolitic materials and drugs, can be simultaneously administrated to humans without direct modification of their individual effects, which is very important from the pharmaceutical point of view
4) Demonstration of the potential use of natural clinoptilotite (NZ) as a matrix for the slow release of ions of pharmaceutical interest. The temporal evolution of NZ and K- and Li-enriched forms of this zeolite in aqueous medium through conductometric and pH-metric techniques, complemented by atomic absorption spectrometry has been examined. It is concluded that simple electrochemical tools are able to reveal in a fast and inexpensive fashion some details of the various phenomena taking place in the system as time goes by. Both potassium and lithium ions are commonly employed in the treatment of cardiovascular dysfunctions and psychiatric disorders, respectively. The studies carried out can be regarded as a first step for the use of natural clinoptilolite as an ions release matrix to be applied in animals and in humans.
5) Demonstration of the potential use of natural clinoptilolite (NZ) as a slew-release drug carrier. A new potential application of purified natural clinoptilolite, NZ, was explored: its drug-carrying capabilities assisted by use of surfactants. The development of support systems of drugs starting from natural clinoptilolite, national product and of abundance in Cuba, it is without doubts a thematic of great interest for the preparation of new formulations. Three kinds of surfactants (cationic, anionic and non-ionic) were employed for the obtainment of different surfactant/natural zeolite composites. Amongst the diffarent surfactants under study, NZ shows the strongest affinity for the cationic surfactant benzallkonium chioride (BC), widely used in the pharmaceutical industry, resulting in the composite labeled NZ-BC. From the two drugs whose interaction with the NZ-BC composite were studied, the strongest affinity was found for the least polar drug, i.e., sulfamethoxazole. NZ demonstrated to be structurally stable after incorporation of BC and sulfamethoxazole. The release assays showed that approximately 80% of the sulfamethoxazole was released from the NZ-BC- sulfamethoxazole system in about 24 h.
6) Contribution to the discovery of new effects in granular matter. A completely new phenomenon in granular matter was discovered: the breaking of symmetry during the process of formation of a sandpile. Instead of forming "disordered" avalanches, the sand falls as a "river" which rotates around the pile either clockwise or counterclockwise. The phenomenon was fully characterized and some macroscopic features of it were explained using a simple kinematic modal.