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UNIT VII, , CHAPTER 8.1, , Non-textile Uses of Dyes, , , , , , The dye stuffs are mainly used for application on textile materials., However, they can also be used for colouring other substrates such as, paper, leather, plastics, foods, drugs, cosmetics, etc. They also find, application in colour photography. The dyes used for these substrates, , . have chromophores and auxochromes similar to those in textile dyes., However, certain special properties may be required depending on the, nature of the substrate. In some case, the higher fastness properties may, be desired, whereas in other cases, brightness may become more, important. Thus, an appropriate class of dye is necessary for a particular, type of substrate. The dyeing conditions required for these substances, , will also be different., 8.1.1 Biomedical Uses of Dyes, , A brief account of dyes having biological and medicinal applications, is given below., , (a) Dyes Used in Formulations, , The drugs either singly or in combination is administered in three, , formulations, i.e., tablets, capsules or syrups. The basic objectives of, colouring these formulations are:, , (i) To enhance the aesthetics of the tablets/capsules/syrups, Gi) To help in the product identification., , 144
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n-textile Uses of Dyes, 145, , No!, iii) The i, ii) The colour coating helps in maintaining the stability of tablet/, , capsule. , iv) Helps to distingui ; :, (iv) ‘aA ie ee between the different formulations available, , (v) It helps the illiterate patients to know which tablet/capsule, should be taken when, on the basis of colour., , Tablets: Some inert materials like starch, chalk, etc. is mixed with, the medicine along with a binder and compressed into a tablet. The tablets, are of two types, 1.€., coated and uncoated. Both of them can be coloured., , Capsules: There are two forms of capsules, i.e., hard shelled capsules, and soft capsules. The capsules are used when the medicine has to be, taken in the form of powder or granules. Both the types of capsules can, be coloured by dyes or pigments. The white pigment like titanium dioxide, makes the capsule opaque., , Syrups: These are thick liquids obtained by dissolving the drugs in, alcohol, glycerol, sorbitol, etc. The syrups are coloured to make them, , attractive. The different syrups can be distinguished by their colours. In, , some cases, the colour is an indication of the flavouring essence added., , Syrup with orange flavour — yellow/orange dye, Syrup with lemon flavour — green/yellow dye, , Syrup with mint flavour — white dye (TiO,), , The dyes used to colour the tablets/capsules/syrups should meet the, , following conditions., (i) They should be FDA/FSSAI approved colour., , (ii), , (iii) They should not cause alle, , The dyes used must be totally non-toxic., rgic reactions., , (iv) They should not interact with the drug., (v) They should not have any physiolgical action them, , (vi) They should be pure and used in very minute amounts., pes of dyes used for colouring tablets/capsules/, , selves., , There are two ty, , Syrups,, (1) Natural dyes or extracts can be used for colour coatings such, , a , -o oe :, S chlorophyll, anthocyanin, carotinoid, turmeric, saffron, etc.
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Introduction to Synthetic Drugs and Dyes, 146, , Natural colouring agents may give a dull, cloudy colour which, (i) Nature, , may be uneven., , (ii) The herbal extracts may interact with the active drug., ii, , 2) Synthetic dyes: The FDA/FSSAI approved synthetic dyes are, wie used to colour tablets/capsules/syrups, ae, , (i) Phthalein dyes (ii) Indigoid dyes, , 9 on, ue CO) ° CO ° HO,S CN, io ! Nv SC, l SO,H, C} COOH HoT, , Enythrosin Indigo Caramine (Indigotin I), , (iii) Azo dyes, , — SO,Na, nao,s-€_)-N=N-—<_N, COONa, Tartrazine, , (iv), , HO, N, or Sw SO,Na, , Sunset Yellow, , (b) Biological Staining Agents, , NaO,S, , Many dyes belonging to azine, thiazone and triphenyl methane class, are used as biological staining agents. Some of these dyes have the property, , of specifically staining certain microorganisms and hence they are useful, in identifying and differentiating these microorganisms., , Methylene blue is the most commonly used stain in bacteriological, techniques for examination of pathogenic organisms such as tuberculosis, and cholera bacilli. Further, methylene blue is used to selectively stain the, , living tissues. For example, it deeply colours peripheral nervous system, \eaving other parts unstained.
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Non-textile Uses of Dyes 147, , (CH,),N7 0 - ea, cr, , Methylene blue, , Christian Gram devised Gram Staining method to classify bacteria, into two types. In this method, the fixed bacterial smear is treated with a, solution of crystal violet and then with iodine solution which reacts with, the dye and the cell constituents. The smear is then washed with alcohol, (decolourising agent) and counterstain such as Safranine-T (red dye) is, added. The bacteria which retain the colour of crystal violet are called, Gram positive bacteria. But those which lose the violet colour and get, counterstained red by Safranine-T, are called Gram-negative bacteria., , +, ee fre eee, C Cl hs NH,, , H,N, C,H; Cr, , N(CH),, Crystal violet Safranine-T, , Tetraiodo and tetrabromo phenolphthalein are used as stains in the, X-ray examination of gall blader and liver respectively. 3-iodo and 4-iodo, alizarine are opaque to X-rays and hence used in X-ray visualization., , (c) DNA Markers, , The special characteristics of any object or living tissue which can, be easily identified are called markers. DNA markers also known as genetic, , markers are defined as follows:, , (i) Any genetic element such as location, DNA sequence or, chromosome feature, which can be readily detected by, moiecular techniques and used to follow chromosome or its, segment during genetic analysis is called DNA marker., , (ii) Any unique DYNA sequence having known location and, associated with a particular trait and used in restriction mapping, experiments to identify that sequence is called DNA marker.
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Introduction to Synthetic Drugs and Dyes, 148, , Imp, , (i), , Saute NA markers in crop improvement:, lications of D, ortant APP, , e useful in the assessment of genetic diversity, , '§ ar 7, DNA marker: and advanced breeding material., , in germplasm, cultivars,, i) DNA markers can be used for constructing genetic linkage, Wl f, , maps., , (iii) DNA markers are useful in identification of new useful alleles, in the germplasm and wild species of crop plants., , (iv) DNA markers are used in marker assisted selection which has, several advantages over straight selection., , (v) DNA markers are useful in study of crop evolution., Several dyes are used in the DNA markers., , 1. Bromophenol blue: This is a triphenyl OH, methane dye, which is structurally related to the Br Br, indicator phenolphthalein. Br, , It is prepared by slowly adding excess no 6-9, bromine to hot solution of phenolphthalein in glacial py szO, acetic acid. Bromophenol blue is used as follows. 4, , (i) As acid base indicator, its useful range lies between 3.0 (yellow), to 4.6 (blue)., , (ii) Colour marker: It can also be used as a colour marker to, monitor the process of agarose gel or polyacrylamide gel electrophoresis., Since bromophenol blue carries a slight negative charge at moderate pH,, it will migrate in the same direction as DNA or protein ina gel. The rate at, which it migrates varies with the gel density and buffer composition. Ina, typical 1% agarose gel in a TBE buffer, bromophenol blue migrates at the, same rate as DNA fragment of about 300 base pairs., , (iii) As a dye: At neutral pH, the dye absorbs red light strongly and, solution appears blue. At low pH, the dye absorbs U.V., and blue light, strongly and solution appears yellow. In the middle of the range at pH 3.6,, the indicator has green-red colour which shifts depending on concentration, and/or path length through which the solution is observed and this, phenomenon is called dichromatic colour. Kraft’s dichromaticity index is, the extent of change in colour hue when the thickness or concentration of, , observed sample is changed. Bromophenol blue has the highest value of, this index, i.e., 10.
