GOLD (Aurum, Au) — an element of the first group of a periodic system of D. I. Mendeleyev, the metal differing in low reactivity thanks to what finds broad application in instrument making, including medical; 3., its alloys and drugs are used in stomatology, oncology, etc. 3. is the main currency metal and one of the base jewelry materials.
3. it is used by the person since the most ancient times: contents it is equal in crust 4,3-10-7 weight. %. It meets in the form of nuggets (or sand), is more rare in the form of tellurides or selenides; particles 3. are often interspersed in quartz rocks. Usually native 3. contains impurity of silver, copper, platinum, bismuth, iron. 3. it was revealed also in plants, in horns and hoofs of the animals growing or living in gold-bearing areas. In minute quantities 3. contains in water of the World Ocean (in water of its polar oceans more, than in water of southern).
Sequence number of gold 79, atomic mass 196,967. Natural 3. — metal of yellow color, consists of one, almost stable isotope. The period of its half-decay apprx. 3*10^16 years. Density 3. at 20 ° 19,32 g/cm 3 , t ° pl 1064,4 °, t ° kip 2947 °. 3. has big conductivity, a high malleability and viscosity. Beaten gold (a gold foil) illuminates 0,0001 mm thick in aeruginous color. 3. directly does not connect to oxygen, it is steady on air and in water.
In strong to-takh (nitric, sulfuric, etc.) 3. it is dissolved only in the presence of strong oxidizers (HIO 3 , MnO 2 ); 3. it is dissolved also in hot anhydrous selenic to - those, in mix nitric and salt to - t (aqua regia) and in saturated with chlorine salt to - those. 3 are easily dissolved. in solutions of cyanides of alkali metals. Use this property for its extraction even from lean ores. Being dissolved in mercury, 3. forms amalgam; with many metals it forms alloys. Alloys 3. with silver, copper, cadmium, zinc and platinum are applied in stomatology. At recovery of the diluted solutions 3., and also at their electric spraying by a method of Brediga colloid solutions 3 turn out., which coloring depends on degree of its dispersion. In chemical connections 3. there can be one - and trivalent. Connections trivalent 3. are steadier. 3. can form complex connections, in particular complex salts, napr, aurates — complex salt to - you are H [Au(OH) 4 ], chloraurates — zolotokhloristovodorodny complex salt to - you are H (AuCl 4 ) • 4H 2 O. From numerous salts of this to - you the greatest practical value have sodium chloraurate — Na (AuCl 4 ) • 2H 2 O, so-called gold salt, auronatry chloride. Salts 3., its colloid solutions and organic compounds of a bakteritsidna. Salts 3. are also specific inhibitors (see) some enzymes. Soluble salts 3. affect skin prizhigayushche. Metal 3. and its connections were used for intravenous and intramuscular injections at treatment of some infectious diseases, kollagenoz, etc. Drugs 3., entered parenterally, rather quickly resolve, collect preferential in lungs and kidneys, are actively englobed by cells of reticuloendothelial system, in blood are found only in plasma. Salts 3. are used at gistol, methods of a research (see. Gilding methods ).
At long contact of the person with 3. and its connections (e.g., during the work on jewelry productions, etc. in certain cases noted developing of specific allergic dermatitis; solutions of salts 3. have the expressed toxicity for an organism.
Radioactive gold and its clinical use
3. has a number of artificial radioisotopes with various mass numbers: 194 Au, 195 Au, 196 Au, 197m Au, 198 Au, 199 Au, 200 Au.
B to medicine apply 3., marked isotope 198 Au. Receive it at neutron radiation natural 3. on reaction 197 Au (n, γ) 198 Au, section of reaction 98,9 barn.
Half-life 198 Au makes 2,698 days. In the course of disintegration there is an emission of electrons to energy of 0,29 Mev (1%); 0,96 Mev (99%); 1,38 Mev (0,025%) and gamma quanta with energy of 0,412 Mev (96%); 0,677 Mev (1%); 1,09 Mev (0,2%). The ratio of the stable carrier and isotope in the irradiated target reaches 109, ud. radioactivity — not less than 100 mkyuri/mg.
Radiation dosimetry 198 Au in practice carry out by detection of gamma quanta with energy of 0,412 Mev or electrons with energy of 0,96 Mev (see. Dosimetry of ionizing radiation ).
In biology and medicine use only drugs metal 3. marked isotope 198 Au, in the form of the colloid solutions stabilized gelatinous, and 3. in the form of pins (granules). About receiving and the first experience a wedge, uses of colloid solutions radioactive 3. reported in 1946. Hahn and Sheppard. They paid attention on 198 Au because metal colloid 3. it was physiologically inert and did not cause side reactions; receiving isotope 198 Au is very economic, and the period of its half-decay met requirements of production and clinical physicians. Existence of beta and gamma radiations allowed to create high fabric doses of radiation by means of isotope and it is easy to observe localization of isotope in bodies and fabrics.
Colloid solutions 3. enter in circulatory and limf, vessels, subcutaneously, intramusculary, into tumors and the fabrics surrounding them, into serous cavities and cavities of joints. To a raya it is rare, hl. obr. in the research purposes, apply other ways of administration of colloid solutions 3. in an organism. Pins (granules) with 198 Au implant into tumors and the fabrics surrounding them. Key feature of colloid solutions radioactive 3., as well as other colloids, their deposition in cells of reticuloendothelial system and on structures of connecting fabric is. At the same time in case of introduction in limf, or circulatory systems drug is deposited only with reticuloendothelia, being englobed by cellular elements limf, nodes, a liver, a spleen, marrow. In case of intracavitary or interstitial injections the main amount of drugs 3. communicates fibrous structures and the main substance of connecting fabric, to 15% of drug it rezorbirutsya from fabrics in limf, system with the subsequent deposition in a reticuloendothelium regional limf, nodes, a liver, a spleen (similar to behavior of drug at an injection directly in limf, system). Important characteristic colloid 3. concentration of colloid particles in drug is. Drugs with an average diameter of colloid particles of 5 — 13 nanometers and concentration 3 with other things being equal differ in the highest concentration of particles. to 6 mg/ml. In the practical purposes it is enough to consider only concentration 3. in working solution of drug in mg/ml. The high-concentrated drugs 3. rezorbirutsya more intensively from fabrics in limf, the system also is more evenly filled by the interconnected groups limf, nodes. Cultivation of drug 3. solutions of novocaine or isotonic solution of sodium chloride significantly reduces a resorption of a colloid in limf, system, at the same time the insignificant amounts of drug which came to a lymph hl are absorbed. obr. in the first limf, a barrier that can be mistakenly regarded as a sign of defeat overlying limf, nodes.
The deposited colloids 3. practically are not brought out of an organism, and the means promoting removal of colloids 3. from an organism, no. Pins (granules) 3. in the field of implantation are not brought out of fabrics.
Selective deposition of colloid particles 3., containing isotope 198 Au in cellular elements of a reticuloendothelium and structures of connecting fabric, is a basic basis of use of drugs 3. from diagnostic and to lay down. purposes. At the same time quantitatively deposition 3. bodies and fabrics estimate by registration of gamma quanta with energy of 0,412 Mev; to lay down. the effect is provided with beta radiation 198 Au with energy of electrons of 0,96 Mev. Lech. effect at use of pins (granules) with 198 Au is defined by the gamma radiation of isotope, electrons are absorbed by the special platinum filter of a pin.
Apply colloid solutions 3 to radio isotope diagnosis. with various sizes of colloid particles — 10 — 13 and 20 — 30 nanometers at concentration 3. to 6 mg/ml and radioactive concentration to 60 mkyuri/ml (see. Radioactive colloids , Radioactive drugs ). As diagnostic means colloid 3. apply to scanning and definition of a blood-groove in a liver, definitions of a condition of function of reticuloendothelial system, definition of a regional lymph flow and scanning limf, nodes (see. Radio isotope diagnosis ).
With to lay down. the purpose apply colloid solutions 3. as with homogeneous dispersion, and unequigranular. Radioactive concentration of the administered drug shall not exceed 4 mkyuri/ml that is reached by cultivation of initial drug 0,25 — 0,5% solutions of novocaine or isotonic solution of sodium chloride. Interstitial administration of drug is applied at treatment of small tumoral nodes (a tumor of skin, a mammary gland, etc.) when other methods of treatment cannot be used, in addition to other methods radiation therapy (see). Drugs enter also into the remains of a tumor and surrounding fabrics at not radical operative measures. Intracavitary administration of drugs 3. in serous cavities and joint bags apply as a palliative action for the purpose of reduction of exudation, and also with the preventive purpose after operations for malignant new growths stomach (see), intestines (see), ovaries (see) or lungs (see) for impact on possible dissimination of tumoral elements on serous covers. Vnutrilimfososudisty introduction colloid 3. apply to preventive beam impact on possible lymphogenous micrometastasises at the combined treatment predictively of adverse tumors (a melanoma, a breast cancer, cancer of a penis, etc.), and also at treatment of systemic lesions limf, nodes (a lymphogranulomatosis, a lymphosarcomatosis, etc.).
At treatment of small tumoral nodes instead of colloid 3. apply pins (granules) with isotope 198 Au.
In medical - biol, researches colloid solutions 3. apply hl. obr. for studying of function of reticuloendothelial system and a regional lymph flow.
Bibliography: Voynar A. I. A biological role of microelements in an organism of animals and the person, page 307, M., 1960; Ivanov I. I., etc. Radioisotopes in medicine and biology, M., 1955; Nasonova V. A., etc. Pharmacotherapy in rheumatology, page 159, M., 1976; P and - sir R. and Chetyanui. Inorganic chemistry, the lane from Romanians., t. 2, page 752, M., 1972.
E. A. Maksimyuk; S. V. Sery (I am glad.).