CHAPTER 2 CURATIVE MEDICAL TEXTILES REVIEW

Transcription

1 9 CHAPTER 2 CURATIVE MEDICAL TEXTILES REVIEW 2.1 INTRODUCTION The curative textiles arena is the highlighted newborn area of medical textiles. Though the literature specific to the curative textiles is not rich, there have been many research works related to textiles coated with herbal products and chemicals. Curative textiles are a merger between textiles and curative components. Curative textiles can be broadly classified into two types: curative function performed by the regular textile material and textiles augmented with external curative components. The curative components could either be a natural product or a synthetic compound. The era of multifunctional textiles started with the introduction of antimicrobial textiles. Compounds with antimicrobial activity would add an additional functionality to the textile material. But such textiles cannot be considered as curative textiles as their role is mainly preventive in nature and their support is only secondary to the healing process. In case of curative textiles, the role played by the multi-function textiles is vital and primary. The developments in the field of coated textiles were made possible due to the development in the coating and processing technologies. The coating method is crucial in order to deliver the coated component in the right way. Starting from dip-dry and pad-dry-cure processes to the recent nano particle-coating process, there has been an enormous improvement in the field. With the advent of concepts such as eco-friendliness and bio-

2 10 compatibility herbal products are being preferred over synthetic chemical compounds. The herbal components have also low side effects compared to the synthetic chemicals. The extraction methods used in the herbal medicinal system have vastly grown. Sophisticated instruments and precise characterizations have been put in place. Since herbal medicines are related to human health, a high degree of accuracy is required in their characterization. Advanced chromatography and spectrometry techniques are being used at all levels. Application of curative textiles and their evaluation is also of equal importance. Though the necessity for the evaluation is high, there are only a few methods available for the evaluation. The need for innovation in the evaluation methods for the curative textiles has to be addressed. 2.2 MEDICAL TEXTILES Medical textile is one of the emerging areas in the field of technical textiles. Sanitary napkins, incontinence diapers, surgical bandages, wound dressings, healthcare textiles, sutures, vascular grafts, heart valves, artificial tendon, artificial joints, artificial kidneys are examples of medical textiles. Surgical bandages and various dressings are classical examples of textiles used in the treatment of ailments. Developments in textile based dressings with self-healing property have been tried by coating them with several chemical and natural products thus making them take the functional role (Gupta et al 2010). Dressings such as adhesive dressings, collagen dressings, composites, hydrogel and hydrocolloid dressings, alginate based dressings, burn therapy dressings are commercially available. 2.3 SURGICAL BANDAGES Surgical Bandages are also called as Medical Devices. Bandages could be elastic as well as non-elastic. Based on the function and properties

3 11 bandages can be classified into three major categories namely, fixation, support and compression. Fixation bandages are elastic in nature and they are used to hold the dressings or medicaments in place. Support bandages are used to provide support to tissues and ligaments. Compression bandages can be classified again depends on the amount of compression it produces Compression Bandages Compression therapy is used in treating phlebological and lymphological disorders such as varicose veins, leg ulcers, eczema and oedema (Bleckena et al 2005) and other musculoskeletal disorders. The most common practice used by medical practitioners in the compression therapy is the usage of compression bandages. Based on the amount of compression required for the treatment, the stretch of the bandage is determined. Resting pressure applied on the affected part by bandage creates compression enabling the venous pressure to be regulated. The blood flow in the vein is controlled and there by the disorders is managed. Use of compression bandages in the treatment of venous ulcers has been reviewed thoroughly (Cullum et al 1997; Lee et al 2006). Such bandages come under Class 1 medical devices. Compression bandages are classified based on four important aspects such as pressure, number of layers, components and elastic properties (Partsch et al 2008). Elastic compression crepe bandages are termed long stretch bandages and the elasticity, as per DIN standards, is defined as the percentage elongation of the material following application of a force of 10 N/cm width of the bandage. The pressure developed beneath a compression bandage is governed by the tension in the fabric that is exerted when the bandage is applied. One way of creating fabric tension is by using the stretch yarns and the other method is by using textured and crimped inelastic yarns (Cooper et al 1965) and thus extensibility of the bandage plays the major role in imparting pressure and is an indication of the ability of compression.

4 Fixation Bandages Fixation bandages are simple elastic bandages and take the profile of the body part and are also called as Contour bandages. They have high elasticity and have open structure. They are normally applied as a second layer over a wound dressing. They are multi-purpose bandages and can be used for various bandaging applications Narrow Weaving This form of weaving is used normally for tapes and bandage fabrics. The width of the fabric ranges from 1 cm to 20 cm. The loom is also called as needle loom due to its weft insertion mechanism which involves a reciprocating needle on a cam. The warp yarns can be let off from beams as well as from creels. The weft is inserted as a double-pick. The selvedge can also be secured at one end by a crotchet stitch using a binder yarn and a needle. The looms are capable of high-speed weft insertion with 900 double picks per minute Coated Bandages and Coating Methods Bandages as substrate are also coated to enhance the amount of compression and also to widen their functionality. Zinc-Paste bandages, cohesive and adhesive bandages are examples for such bandages. Besides the coated compression bandages, there exist also medicated wound dressings. The coating could either be the synthetic chemicals, latex /rubber or medicinal products. Shear spreading, dip-dry, pad-dry-cure and spray drying are the common methods used for coating the additives on the bandage surface. Microcapsules can be coated on textile surfaces in various ways and this section discusses them in detail. Conventional coating methods such

5 13 as blade-on air, blade-on-roll, screen coating and dosing roller have been discussed by Ghosh (2006). Printing and digitial coating can also be used for coating microcapsules on textiles. Dip-dry, pad-dry-cure, spray coating, printing, Textiles coated with silver are used in the treatment of atopic dermatitis (Haug et al 2006). Antiseptic, antimicrobial and anti-inflammatory effects have been observed in the silver coated textiles. 2.4 PLANT RESOURCES Plants are a sustainable source of medicinal products especially in traditional medical practices. Plants contain active substances such as alkaloids, tannins etc., produced during their secondary metabolism which serve as a potential reservoir of medicinal products (Bourgaud et al 2001; Parr 1989; Croteau et al 2000). There are number of methods such as solvent extraction and steam distillation to extract the active substances from the plant parts (Ong Eng Shi 2004; Mukherjee 2002). The traditional method of extracting oils (medicial tars) from the woody parts such roots, stem bark and branches has been reported by Kargioğlu et al (2010), Julin (2008), Lindborg (2009). The traditional practitioners of Indian medicine extract the stem part of medicinal plants by a crude pyrolysis method and use the extracted oily substance in the treatment of pain, inflammation and other musculoskeletal disorders. There are numerous medicinal plants available for the treatment of diseases ranging from headache to cancer Secondary Metabolites (Tolonen 2003) Secondary metabolites of plants are found only in certain species and family. The presence of a particular metabolite is specific to that plant species. The production of such metabolites depends on the environment of the plant or the available nutrition. They may provide protection against pests,

6 14 animals or UV radiation. Some of the secondary metabolites may be pharmacologically active in humans and useful as medicines or food additives. Some well known examples for such secondary plant metabolites are the analgestic and antipyretic compound salicin which is used in the synthesis of acetylsalicylic acid (aspirin), the anticancer drug taxol and a strong addictive and narcotic compound morphine isolated from morphine. Major classifications of secondary metabolites are phenoloics (eg. Flavonoids), alkaloids and terpenoids Flavonoids Flavonoids are the most extensively distributed phenolic compounds of the plant kingdom. They are found in all parts of the plant as a complex mixture with different chemical compounds. They have a three carbon link in their backbone. The C 6 -C 3 -C 6 structure renders them hydrogen and electron donors. Flavonoids are free radical scavengers and they can effectively retard cell aging process and can protect humans against cancer and cardiovascular diseases (Shahidi 1997). Figure 2.1 Basic structure of flavonoids

7 15 Flavonoids have three rings in their structure (Figure 2.1) and the antioxidant property of the flavonoids is due the hydroxyl substitution of the A- and B- rings and the substitution pattern of the C-ring (Tsimogiannis et al 2007; Dangles et al 1999). According to the structure of the C-ring, flavonoids can be categorized into five major subgroups: flavanols, flavones, flavanonols, flavanones and flavanols (Hermann 1988) Terpenes and Terpenoids Terpenes contribute to about 55% of the total secondary metabolites (Croteau 2000). The term terpene refers to a hydrocarbon molecule while the term terpenoid refers to a terpene that has been modified such as addition of oxygen. Isoprene is the building block of plant secondary metabolites. The isoprene unit can build upon itself in different ways in a five-carbon molecule. The single isoprene unit represents hemiterpenes (C 5 ). Terpenes with two isoprene units are called as monoterpenes (C 10 ). Sesquiterpenes (C 15 ) have three isoprene units and diterpenes (C 20 ) and triterpenes (C 30 ) have two and three terpene units respectively. Distribution of terpenes in the heartwood of trees has been extensively studied (Thompson et al 2006; Martin et al 2003; Semiz et al 2007). Terpenes have been used in various fields. Terpenes are found to have antimicrobial property (Islam et al 2003). Plant oils containing terpenes have shown inhibitory effects against various species of bacteria (Prabu Seenivasan et al 2006). Terpenes have been incorporated into antibacterial soaps, cosmetics and household products. Absorption and penetration of terpenes into human skin has been analysed by Cal et al (2000) Alkaloids Alkaloids are secondary plant metabolites with nitrogen group. Many of these metabolic by-products are derived from amino acids and

8 16 include an enormous number of nitrogenous products. There are more than 10,000 different alkaloids identified from over 300 different families (Raffauf 1996). Some alkaloids have structural similarities with neurotransmitters in the central nervous system of humans, including dopamine, serotonin and acetylcholine. The effect of these alkaloids led to the development of painkiller medications. Alkaloids are broadly classified into two categories viz., pseudo and true alkaloids. True alkaloids have nitrogen in a heterocyclic ring and they are again subdivided into indole alkaloids, steroidal alkaloids, quinoline alkaloids, pyridine alkaloids, pyrrolidine alkaloids, tropane alkaloids, iso-quinoline alkaloids, cyclopeptide alkaloids, phenanthrene alkaloids, phenethylamine alkaloids and purine group etc (Cordell 2008). The classification is based on the amino acid from which they rise. The heterocyclic ring structures are given in Figure 2.2. Figure 2.2 Heterocyclic ring structures of alkaloids

9 Dodonaea viscosa (L) Jacq Dodonaea viscosa (L.) Jacq.is an evergreen shrub widely found in tropical and subtropical regions, and it has been used in traditional medicines in various countries (Anilreddy 2009; Chopra et al 1985; Sandhya Rani et al 2009). Medicinal use of Dodonaea viscosa in tribal and traditional medicine in various regions of India and other countries has been reported, especially for curing pain and swelling due to rheumatism, waist pain and gout (Ali et al 2004; Bharath Kumar and Surya Naryana 2010; Ibrar et al 2007; Meena et al 2009; Parkash and Aggarwal 2010; Ram et al 2007; Reddy et al 2009; Venkataswamy et al 2010).Bark extracts have been used in astringent baths and fomentations to relieve problems, including rheumatism and gout (Amabeoku et al 2001). The tribes in the Maruthamalai area of Tamilnadu (the location of this present study) crush the stem and tie it to fractured bones to speed up bone setting (Senthilkumar et al 2006). Australian aborigines fumigate a person by burning the stems, bark and leaves of Dodonaea viscosa to alleviate pain (Wagner 2005). Although the plant is rich in phyto-chemicals, most of the research on Dodonaea viscosa has focused on its flavonoids (Pengelly, 2008). In addition to flavanoids (Ghilselberti 1998; Sachdev and Kulshreshtha 1983, 1986), coumarins and lignocoumarins (Hemlata and Kalidhar 1994) as well as saponins (Wagner et al 1987) and tannins (Sastry and Nayudamma 1966) have been isolated from Dodonaea viscosa. Rojas et al (1996) isolated antispasmodics, sakuranetin and kaempferyl from the stem of Dodonaea viscosa. Antidiarrhoeal (Rajamanickam et al 2010), anti-diabetic, hypolipidaemic and antioxidant properties (Veerapur et al 2010) have also been reported in Dodonaea viscosa.

10 Ziziphus jujuba Ziziphus jujuba belongs to the family Rhamnaceae. They are semi deciduous and much branched medium sized trees. The bark of the tree has deep longitudinal furrows and is grayish brown or reddish in color (Mahajan and Chopda 2010). Ziziphus jujuba is rich in phytochemicals and thus has various traditional medicinal uses. The fruit of the plant is rich in Vitamin C, B1 (thiamine), B2 (riboflavin) (Kuliev and Guseinova 1974) and Pectin A (Tomoda et al 1985) and possesses anti inflammatory, antioxidant and antibacterial properties. Stem bark of the plant contains alkaloids (Pareek 2001). Cyclopeptide alkaloids, mauritine-a, mucronine-d, amphibine-h, nummularine-a and B, jujabine-a and B were isolated from the stem bark of Z. jujuba by Tschesche et al (1976), Tripathi et al (2001) isolated a new cyclopeptide alkaloid jubanine C along with the known cycloalkaloids scutianine C and zizyphine A from the stem barks of Z. jujuba. Z. jujuba contains also sativanines of various classes (Tan and Zhou 2006). Frangufoline, another cyclopeptide alkaloid was isolated from the stem bark of Z. jujuba by Devi et al (1987). Besides alkaloids, a pentacyclic triterpenoid, zizyberanalic acid has also been isolated from the stem barks of Z. jujuba (Kundu et al 1989). Lee et al (1996) isolated three more triterpene esters, 2-O-protocatechuoylaliphitolic acid, 2 -hydroxypyracrenic acid and 3-Oprotocatechuoylceanothic acid from the root part of the plant. Due to the presence of such a wide range of phytochemicals, Z. jujuba has been used in the traditional medicine for a long time. The Cyclopeptide and peptide alkaloids from Z. jujuba were found to show sedative effects (Han et al 1989). The traditional use of the stem barks of the plant for healing wounds is reported by Ullah et al (2010). A traditional formulation of barks of Z. jujuba with milk and honey is used to cure diarrhea, dysentery, cough and cold (Jan et al 2008). The leaves of Z. jujuba are used in the treatment of diabetes (Ahmad et al 2009; Inanç et al 2007).

11 Cedrus deodara Cedrus deodara is an evergreen tree prevalent in north of India. Traditionally the heart wood of C.deodara was used to strengthen cerebral functions and nervous systems (Shivanand et al 2009). The anticonvulsant and anxiolytic properties of the extract from the heartwood have been reported. The heart wood is reported to have phytochemicals such as alkaloids, glycosides, tannins and terpenoids (Agarwal and Rastogi 1989) Moringa oleifera Moringa oleifera is a soft perennial wood native of India, Pakistan, Bangaladesh and Afghanistan. All parts of the tree are edible and used in the traditional medicine for centuries as anti-tumour, anti-pyretic, anti-spasmodic and anti-cardiac agent (Fuglie 2001). Phytochemicals such as tannins, saponins, flavonoids, glycosides, terpenoids are present in leaf extracts of M.oleifera (Nepolean et al 2009) Celastrus paniculatus Celastrus paniculatus is a climbing shrub used in the traditional medicine. The seed contains saponins and sterols and used as antiinflammatory agents (Sudha Parimala et al 2009). The seed oil is used externally for massaging for treating diseases like arthritis, paralysis, lumbago and facial palsy (Lekha et al 2010). 2.5 MUSCULOSKELETAL DISORDERS Musculoskeletal disorders can be defined as the disorders of the muscles and their associated ligaments and other connective tissue and of the bones and cartilage viewed collectively. Muscle is a tissue made up of

12 20 contractile cells which are capable of producing movement or tension. Human body contains three types of muscles namely skeletal, cardiac and smooths (Knight and Biswas 2003) Categories Bone diseases, cartilage diseases, fasciitis, foot deformities, foot diseases, hand deformities, jaw diseases, joint diseases, muscular diseases, musculoskeletal abnormalities, rheumatic diseases and tennis elbow are some of the categories of musculoskeletal disorders. In musculoskeletal system, disorders of soft tissues (muscles, tendons, ligaments, fascia, capsules etc.,) are in most cases considered separately from those of the hard tissues such as bones and cartilage (Sambrook 2001) Arthritis (Clough 2006) Arthritis is a condition of inflammation in one or more joints. Arthritis may also result in swelling, redness, tenderness, stiffness or unusual warmth only in joints. At advanced stages, arthritis is severely painful may cause joint destruction and permanent disability. Arthritis is different from the joint pain which is called as arthralgia. Arthritis is a disease and not a symptom for other diseases except rheumatid arthritis where arthritis is considered to be a symptom for rheumatism involving pain in the other tissues along with joints. Rheumatid arthritis, osteoarthritis, gout and spondyloarthropathies are some of the form of arthritis. Treatment methods for arthritis include occupational therapy, chemotherapy and surgery. Antiinflammatory agents, antibiotics, immunosuppressive medicines (medicines that inhibit the immune system), uric acid-lowering agents and corticosteroids are used in the chemotherapy.

13 21 Various herbs have been used in the treatment of arthritis. Hochberg (2008) has discussed some nonconventional methods including Chinese acupuncture and herbal products to treat osteoarthritis. Venkatesha et al (2011) have tried various herbal medicinal products which have antiarthritic property in the treatment of rheumatoid arthritis (RA). Herbal ointments were applied on hands and knees of patients suffering from osteoarthritis and the treatment has shown improvement in pain and stiffness (Gemmel et al 2003) Rheumatism Dorland's Medical Dictionary for Health Consumers (2007) defines rheumatism as any of a variety of disorders marked by inflammation, degeneration, or metabolic derangement of the connective tissue structures, especially the joints and related structures, and attended by pain, stiffness, or limitation of motion. Rheumatism may include back pain, shoulder pain, neck pain, arthritis, inflammation, swelling, rheumatic heart disease, rheumatic fever, tendinitis and spondylitis. Treatment methods for rheumatism include non-steroidal and antiinflammatory drugs (NSAIDs) and analgestics. Medicinal herbs have been used in the treatment of rheumatism (Adams et al 2009; Chou and Chang 1998, Setti and Sigal 2005) Oedema Oedema is the accumulation of fluid in extra-vascular tissue as a result of complex interactions involving the permeability of capillary walls and the hydrostatic and oncotic pressure gradients that exist between the blood vessels and surrounding tissue. Starling s equation suggests that the application of external compression will counteract the loss of capillary fluid

14 22 by increasing local tissue pressure and reinforce reabsorption by squeezing fluid into the veins and lymph vessels. This in turn will help to resolve oedema. Depending upon the amount of pressure applied, a compression bandage may influence the internal volume of veins, arteries and lymph vessels. Structures near the surface of the skin are compressed more than the deep vessels. This is because the compressive force is partly dissipated by compression of the surrounding tissues. Nuclear medical investigations have shown that compression removes more water than protein from the tissue, increasing oncotic tissue pressure. This results in a rapid reaccumulation of oedematous fluid if compression is not sustained Venous Disorders Varicose veins are dilated, tortuous, elongated superficial veins that are usually seen in the legs. They appear as lumpy, winding vessels just below the surface of the skin. There are three types of veins, superficial veins that are just beneath the skin, deep veins that are large blood vessel found deep inside muscles, and perforator veins that connect the superficial veins to the deep veins. The superficial veins are the blood vessels most often affected by varicose veins and are veins seen by eye when the varicose condition has developed (Alexander et al 1998). The inside wall of veins have valves that open and close in response to the blood flow. When the left ventricle of the heart pushes blood out into the aorta, it produces the high pressure pulse of the heartbeat and pushes blood throughout the body. Between heartbeats, there is a period of low blood pressure. During the low pressure period, blood in the veins is affected by gravity and wants to flow downward (Figure 2.3).

15 23 (Source: Figure 2.3 Illustration of varicose veins The valves in the veins prevent this from happening. Varicose veins start when one or more valves fail to close. The blood pressure in that section of vein increases, causing additional valves to fail. This allows blood to pool and stretch the veins, further weakening the walls of the veins. The walls of the affected veins lose their elasticity in response to increased blood pressure. As the vessels weaken, more and more valves are unable to close properly. The veins become larger and wider over time and begin to appear as lumpy, winding chains underneath the skin. Varicose veins can develop in the deep veins also. Varicose veins in the superficial veins are called primary varicosities, while varicose veins in the deep veins are called secondary varicosities (Berkow and Robert 1997)

16 24 There is no cure for varicose veins. Treatment falls into two classes namely relief of symptoms and removal of the affected veins. Symptom relief includes such measures as wearing support stockings and compression bandages (Figure 2.4), which compress the veins and hold them in place. This keeps the veins from stretching and limits pain. Surgery is used to remove varicose veins from the body. It is recommended for varicose veins that are causing pain or are very unsightly, and when haemorrhaging or recurrent thrombosis appear. Injection therapy is an alternate therapy used to seal varicose veins. This prevents blood from entering the sealed sections of the vein. The veins remain in the body, but no longer carry blood. (Source: Figure 2.4 Application of compression bandage in the treatment of venous disorders Transdermal Delivery System Skin is the human body s largest organ. It is a powerful system that has inherent capacity to renew and heal itself. Skin is a permeable membrane

17 25 allowing transdermal migration of substances. The migration allows delivery of active ingredients by means of the skin. Skin acts as the effective medium from which absorption of the active material takes place. Topically applied creams and ointments with formulations that get delivered by the absorption through the skin are commonly applied transdermal system. The absorption of the active ingredients varies with the psychological factors like stratum corneum layer of the skin, site of application on the body, skin condition and disease, age of the patient, skin metabolism, peeling of the surface skin, sensitivity of the skin and human race. Formulations and carriers also influence the transdermal bio availability (Kumar and Philip 2007). Suruse et al (2009) have attempted to develop herbal extracts based antiinflammatory transdermal system. 2.6 EXTRACTION METHODS Depending on the plant part to be extracted and the plant secondary metabolite, there exist a variety of extraction methods (Mukherjee 2002). Marceration, digestion, solvent extraction, soxhleation, ultrasonic extraction, extraction using electrical energy, percolation, decoction, steam distillation and super critical fluid extraction are some of the methods available for extraction. A few important extraction methods have been discussed in this section Hot Continuous Extraction Soxhletion Soxhletion is the process mainly used with pure solvents to prepare crude plant crude extracts. Soxhlet extractor (Figure 2.5) is used in this method. The material to be extracted is placed in a thimble made of cellulose or cloth in a central compartment with a siphoning device and a side-arm both connected to a lower compartment. The solvent is placed in a lower

18 26 compartment and a reflux condenser is attached above the central sample compartment. The solvent in the lower container is heated to boiling and the vapour passes through the side arm up to the reflux condenser. The vapour liquefies in the reflux condenser and drips into the thimble containing the material to be extracted. The solvent percolates through the material and the wall of the thimble and the extract gradually collects in the central compartment. Once the height of the extract reaches the top of the siphon, the extract flows down to the lower container and the process repeats and the extract in the lower container gets more and more concentrated. Nikhal et al (2010) have extracted phytochemicals from the leaves of Mangifera indica using soxhletion. Soxhletion was used to extract active substances from the bulbs of Allium sativum (Shakya et al 2010). (Source: J. Wood chem. & Tech,30/1,2010,Pg:31-47) Figure 2.5 Soxhlet extractor

19 Steam Distillation Steam distillation is the most widely used extraction method for essential oils or volatile oils. Steam distillation can be carried out in a number of ways. One of the methods is to mix the plant material with water and to take the solution to boiling temperature. The vapours are collected and condensed and later the oil is separated from the water. Steam distillation relies on the physical principle that when two immiscible liquids are mixed each liquid behaves as if it were on its own, and exerts a vapour pressure. The total vapour pressure of the boiling mixture is the sum of the partial pressures exerted by the individual components of the mixture. Since boiling commences when the total vapour pressure equals the atmospheric pressure, boiling point is reached at a lower temperature than if each liquid were in its pure state. Steam distillation cannot be used if the mixture contains hydrolysable compounds such as esters or those that are easily oxidized or decomposed by heat. Figure 2.6 shows the schematic diagram of steam distillation process. (Source: Figure 2.6 Steam distillation to extract herbal contents

20 28 Hili et al (1997) have used steam distillation to extract essential oils from various plants for medicinal purposes. Ripe fruits of Coriander sativum L have been extracted using steam distillation method and later the components present in the essential oil were identified using GC-MS method (Anitescu 1999) Pyrolysis Pyrolysis is the subjection of organic compounds to very high temperature to study its resulting decomposition. Biomass pyrolysis is defined as the process during which the biomass undergoes thermal degradation and gets converted into water vapor, gaseous volatiles, tarry volatiles and char (Srikanth and Kolar 2009). Based on the heating rate and vapor residence time of the process, pyrolysis is classified into slow, fast, flash and ultra pyrolysis. Slow pyrolysis is with a heating rate < 50 o C/min during which primary wood degradations starts at about 230 o C, fast devolatilisation rates are attained at about 300 o C, and the process is practically terminated at 430 o C (Gómez, 2006). The biomass conversion has been analyzed in detail by Bridgwater (2004). The mechanism of conversion of cellulose has been studied by Mamleev et al (2009). Hosoya et al (2009) gives detailed information about the formation of char during the biomass pyrolysis process. Srikanth and Kolar (2009) have studied the kinetics involved in the thermal degradation of various wood components such as lignin and hemi cellulose during pyrolysis. White and Dietenberger (2001) have summarized various kinetic parameters involved in wood pyrolysis. Pyrolysis can be utilized to convert biomass to a product that is used both as an energy source and a feedstock for chemical production (Dinesh Mohan et al 2006). Pyrolysis has been widely employed for converting biomass into fuels. There are extensive studies involving the

21 29 pyrolysis of plant material for the production of bio-diesel (Khor et al 2009; Seng et al 2006) 2.7 EXTRACT CHARACTERIZATION METHODS The plant extracts can be characterized using many qualitative and quantitative methods. Few of the advanced characterization techniques are discussed in this section Gas Chromatography-Mass Spectrometer (GC-MS) Analysis Gas chromatography/mass spectrometry is the synergestic combination of two powerful analytic techniques. The gas chromatography separates the components of a mixture. The mass spectrometer provides information that helps in the structural identification of each component. The two instruments are connected using an interface Gas Chromatogram (GC) A mixture of compounds to be analysed is initially injected into the GC where the mixture is vaporized in a heated chamber. The gas mixture travels through a GC column, where the compounds become separated as they interact with the column. Those separated compounds then immediately enter the mass spectrometer Mass Spectrometer (MS) All mass spectrometers consist of three distinct regions Figure ) Ionizer 2) Ion Analyzer 3) Detector

22 Ionizer (Source: Figure 2.7 Schematic representation of a GC-MS system In the GC-MS discussed in this introduction, the charged particles (ions) required for mass analysis are formed by Electron Impact (EI) Ionization. The gas molecules exiting the GC are bombarded by a highenergy electron beam (70 ev). An electron which strikes a molecule may impart enough energy to remove another electron from that molecule. Methanol, for example, would undergo the following reaction in the ionizing region: CH 3 OH + 1 electron CH 3 OH electrons EI Ionization usually produces singly charged ions containing one unpaired electron. A charged molecule which remains intact is called the molecular ion. Energy imparted by the electron impact and, more importantly, instability in a molecular ion can cause that ion to break into smaller pieces (fragments). The methanol ion may fragment in various ways, with one fragment carrying the charge and one fragment remaining uncharged. For example: CH 3 OH +. (molecular ion) CH 2 OH + (fragment ion) + H. (or) CH 3 OH +. (molecular ion) CH 3 + (fragment ion) +. OH

23 Ion Analyzer Molecular ions and fragment ions are accelerated by manipulation of the charged particles through the mass spectrometer. Uncharged molecules and fragments are pumped away. The quadrupole mass analyzer in this example uses positive (+) and negative (-) voltages to control the path of the ions. Ions travel down the path based on their mass to charge ratio (m/z). EI ionization produces singly charged particles, so the charge (z) is one. Therefore an ion's path will depend on its mass. If the (+) and (-) rods shown in the mass spectrometer schematic were fixed' at a particular rf/dc voltage ratio, then one particular m/z would travel the successful path shown by the solid line to the detector. However, voltages are not fixed, but are scanned so that ever increasing masses can find a successful path through the rods to the detector Detector There are many types of detectors, but most work by producing an electronic signal when struck by an ion. Timing mechanisms which integrate those signals with the scanning voltages allow the instrument to report which m/z strikes the detector. The mass analyzer sorts the ions according to m/z and the detector records the abundance of each m/z. Regular calibration of the m/z scale is necessary to maintain accuracy in the instrument. Calibration is performed by introducing a well known compound into the instrument and "tweaking" the circuits so that the compound's molecular ion and fragment ions are reported accurately Fourier Transform Infrared Spectroscopy (FTIR) Fourier Transform Infrared Spectroscopy (FTIR) is the preferred method of infrared spectroscopy. In infrared spectroscopy, IR radiation is

24 32 passed through a sample. Some of the infrared radiation is absorbed by the sample and some of it is passed through (transmitted). The resulting spectrum represents the molecular absorption and transmission, creating a molecular fingerprint of the sample. Like a fingerprint no two unique molecular structures produce the same infrared spectrum. This makes infrared spectroscopy useful for several types of analysis Total Internal Reflection When a ray of light passes from a denser medium to a rarer medium, the ray bends away from the normal into the rarer medium and this phenomenon is called refraction. Above a certain angle of incidence called critical angle, the light is completely reflected back into the denser medium and this phenomenon is called total internal reflection Attenuated Total Reflection Attenuated total reflection is a sampling technique used in conjunction with infrared spectroscopy which enables the samples to be examined directly in the solid or liquid state without any further preparation Applications in Textiles FTIR-ATR has been used extensively in textiles for the analysis of the coated surfaces of functional textiles. Surface chemistry of the photocatalytic self-cleaning cotton by coation TiO 2 was studied using ATR-IR (Attenuated total reflection-infrared spectroscopy) (Meilert et al 2005). The surface of polyester grafted with acrylic acid has been characterized using ATR-IR (Kawase et al 1991). There were also reports of the use of attenuated-total-reflectance (ATR) FTIR spectroscopy for the identification of cellulosic fibres and characterisation of their state of degradation (Garside and Wyeth 2004).

25 Antimicrobial Assessment Various test procedures have been used to evaluate the antibacterial activity. Some of the tests used are (Ramachandran et al 2003) Agar diffusion test. Challenge test (Quantitative). Soil burial test. Humidity chamber test. Fouling tests. Agar diffusion test is a preliminary test used to assess the qualitatively by measuring the zone of inhibition. It is not suitable for non diffusive finishes and textile materials other than fabrics. Objective evaluation of the antimicrobial activity is arrived at by making use of the challenge test where in which the difference between the actual bacterial count of the treated and are available from AATCC (USA), DIN(International), JIS (Japan ) and SN(Switzerland). The degree of antimicrobial activity of the active substance is expressed by the terms specific antimicrobial activity and general antimicrobial activity. Antibacterial activity for herbal extracts has been studied in various research works. Mohanasundari et al (2007) have examined the antibacterial properties of ethanalic extracts of herbs using Agar diffusion method. 2.8 MICROENCAPSULATION The theory of microencapsulation, the methods and the applications are discussed in this section.

26 34 Microencapsulation is defined as the application of a thin coating to individual core materials that have an arbitrary particle size range between 5 and 5000 m (Bakan 1986; Hawladar et al 2003). Microencapsulation is widely used in the pharmaceutical and other sciences to mask tastes or odors, prolong release, impart stability to drug molecules, improve bioavailability, and as multi-particulate dosage forms to produce controlled or targeted drug delivery (Wieland-Berghausen et al 2002; Yamuda et al 2001; Bolourtchian et al 2005) Types Methods of microencapsulation include spray drying, sol-gel process, spray cooling, spinning disk and centrifugal coextrusion, extrusion, fluidized bed, coaervation. Gouin (2004) has done an industrial appraisal of these existing technologies. Freital et al (2005) have reviewed the state of the art in solvent extraction/evaporation-based microencapsulation technologies for microencapsulating drugs and vaccines in order to utilize their therapeutic benefits effectively. Various factors influencing the capsule retention in spray drying process of volatile materials in food and pharma industry were discussed by Rosenberg et al (1990) Application in Textiles In textiles, major interest of microcapsulation is in the application of durable fragrances, skin softeners, insect repellents, dyes, vitamins, antimicrobial agents, phase-change materials, medical applications, antibiotics, hormones and other drugs (Nelson 2001). The combination of microcapsules and coatings on textiles allow the introduction of new smart functionalities that often are not possible with any other existing technologies (Ghosh 2006). Ghosh (2006) also discusses about various commercially available microencapsulation technologies for the applications in textile technology.

27 35 Few of the medical textile applications of microencapsulation include drug delivery systems using drug loaded hollow fibre, ion-exchange fibres, fibres with bio-active side-chains and textiles finished with cyclodextrins. Flame retardant cotton has been developed by coating the microcapsules of phosphate as the intumescent formulation of polyurethane-phosphate could not be permanent because of the water solubility of the phosphate (Giraud et al 2002). 2.9 FIELD TRIAL Field trials are important for any product to validate the performance of the product. Field trials for bandages have done on patients to ascertain the therapeutic effect. Bauer bandage study gives insight on the methodologies to conduct field trials for curative bandages. Parameters like hospital, study period, patient group, average age, average time of illness, working protocol, laboratory examinations, replacement of bandages, assessment critical are all important criteria in designing a field trial.