What are Antibacterial Dyes?
Antibacterial dyes are special type of dyes that contain antibacterial agents to inhibit or kill the growth of bacteria on dyed fabrics. These dyes contain substances that help kill or stop bacteria from growing on the fabric. There has been an increased interest in antibacterial textiles, which has led to a rapid development of antibacterial technologies for textiles and polymers in recent years.
The use of antibacterial dye on textile fabrics for protecting clothing started in 1941 for military purposes. In the warm and humid weather of tropical islands, certain textile materials, particularly natural fibres, caused an increase in microbial infections. Antimicrobial dyes have attracted more attention in recent years due to the latest developments in functional textiles, as well as concerns about outbreaks of various diseases.
Bacteria can grow on textiles during their storage and use. Textiles, mainly made from natural fibers, can be easily attacked by bacteria because they hold water, giving a suitable environment for their growth. Such textiles have a bad odor and may cause allergy/infection to the wearer. Various approaches have been attempted for making antibacterial textiles using finishing chemicals. Due to the recent past pandemic situation, the interest in antibacterial textiles is constantly increasing. Antibacterial dyes help to maintain cleanliness and provide additional protection in textiles. Some of the natural antibacterial dye are readily available in nature, while antibacterial synthetic dyes are manufactured through various reactions of intermediates.
Using antibacterial dyes in textiles integrates the dyeing and finishing process and results in a more efficient technique in terms of less water and energy usage. Historically, natural dyes are known to have some antibacterial effects, thus they can be considered as a green eco-friendly substitute. Antimicrobial dyes are designed to enhance the hygiene and functionality of textiles, particularly in areas like medical, sports, and activewear.
List of Antibacterial Dyes:
- Natural dyes
- Naphthalamide dyes
- Phthalazinedione dyes
- Quinazolinone dyes
- Pyrazole dyes
- Sulfonamide dyes
- Chitosan-based antibacterial dye
- Antibacterial azo dyes based on curcumin
Briefly described above each antibacterial dyes.
1. Natural dyes:
Natural dyes are environment-friendly and abundantly available in nature. Some natural dyes possess pharmaceutical activities, such as antifungal, antibacterial and antioxidant. They are derived from plants, animals, and insects. Natural dyes are hailed as an eco-friendly alternative to synthetic dyes because most of them are non-allergic, non-toxic, and biodegradable. Natural dyes have low substantivity towards textiles, and generally, mordanting is required to fix natural dyes on textiles.
Some natural dyes have inherent antimicrobial activity. Four natural dyes, Acacia catechu, Kerria lacca, Quercus infectoria, Rubia cordifolia and Rumex maritimus, were tested against common pathogens E. coli, B. subtilis, K. pneumoniae, Proteus vulgaris and Pseudomonas aeruginosa. Q. infectoria dye was the most effective and showed the maximum zone of inhibition, thereby indicating the best antimicrobial activity against all the microbes tested.
Seven natural dyes showed antimicrobial activities of one or more bacteria, and MICs for three dyes were determined. Certain dyes are able to reduce microbial growth almost completely in the case of Escherichia coli and P. vulgaris. Selected dyes would therefore be valuable for the dyeing of sheets and gowns for hospital use.
Curcumin (turmeric) is a food colourant widely utilised as an antibacterial compound to dye textiles. Curcumin is diferuloylmethane, and studies indicated that curcumin has many functionalities, such as anti-tumor, antiviral, antiseptic, antioxidant, anti-inflammatory, analgesic, and anticarcinogenic activity. Cotton fabric was dyed with curcumin using Iron(II) sulphate as a mordant; the dyed fabric showed antibacterial activity against Gram-positive and Gram-negative bacteria.
Henna (Lawsonia inermis) is a red-orange dye used to dye hairs and textiles. The principal component of henna leaves is 2-hydroxy-1, 4-naphthoquinone. Henna leaves possess many pharmaceutical properties, such as antibacterial, anti-inflammatory, anti-hyperglycemic, and anti-apoptotic. Chitosan-treated wool fabric was dyed using henna dye, and the dyed fabric showed more than 80% bacterial colony reduction.
2. Naphthalamide dyes:
Antibacterial dyes can be synthesised by incorporating napthalamide functional moiety in the structure of the dyes. These naphthalamides dyes showed excellent levelness and fastness. The dyes also demonstrated a maximum of 25 mm zone inhibition against S. aureus bacteria and a good colour range.
Two dyes based on naphthalimide were synthesised and applied to nylon 6. Nylon 6 dyed with thiolbased dye indicated more antibacterial activity than hydroxyl group-based dye.
3. Phthalazinedione dyes:
Numerous methodologies were explored by researchers to make phthalazinedione-based dyes for imparting antibacterial properties to textiles. Phthalazinedione moiety is responsible for the antibacterial activity of such dyes. Dyes derived from 2-(thiazol-2-yl)phthalazine-1,4-diones showed good light, washing, heat, and perspiration fastness and antibacterial activity on polyester fabric.
4. Quinazolinone dyes:
Quinazolinone is a heterocyclic compound widely used in the medical field, and it has various functional properties, such as antibacterial and antifungal activities. A reactive dye based on the quinazolinone was synthesised, which showed antibacterial and antifungal activities on nylon, wool, and cotton. Chloro-subbed quinazolinone colours demonstrated more antibacterial properties than bromo-subbed quinazolinone colours.
5. Pyrazole dyes:
Pyrazole-based dyes are notable for their antibacterial and anticancer properties. The polyester fabric was dyed with azo-pyrazole disperse dyes, and the dyed fabric displayed antibacterial properties. These reactive dyes can give good wash fastness on cotton because of covalent bonding and magnificent antibacterial activity because of the presence of pyrazole moiety. Pyrazole triazine-based disperse dyes were synthesised and applied to polyester.
6. Sulfonamide dyes:
Sulfonamides are used to treat bacterial infections. The excellent performance of sulfonamide makes it an attractive chemical for the synthesis of antibacterial compounds. Dye chemists used the proficiency of this drug to synthesise antibacterial dye. Sulfonamide-based dyes were simultaneously applied with the finishing agent DMDHEU (Dimethylol dihydroxy ethylene urea) on viscose fabric; the treated viscose fabric demonstrated UV protection, crease-resistance, and antibacterial activity.
The polyester dyed with synthesised disperse dye showed wet rubbing fastness rating of 4-5 and antibacterial activity.
7. Chitosan-based antibacterial dyes:
Chitosan is a biopolymer with inherent antibacterial properties and is widely explored in textile finishing. Chemical modification in synthetic dyes through various reactions is a simple way to achieve antibacterial functionality. The amino group of chitosan acts as a site to prepare the antibacterial dye. Chitosan quaternary ammonium salt-based dye showed more antibacterial activity than the reactive red dye.
8. Antibacterial azo dyes based on curcumin:
As discussed in the previous section, curcumin is a compound known for its antibacterial activity. It can also be used to synthesise azo dyes for the simultaneous coloration and antibacterial finishing of textiles. These colorants showed a maximum of 88 % antibacterial activity on silk due to the availability of curcumin in the structure of the dyes.
References:
- Sustainable Textile Chemical Processing Edited by Dr. Javed N. Sheikh & Prof. (Dr.) M. D. Teli
- Functional Textiles for Improved Performance, Protection and Health Edited by N. Pan and G. Sun
- Principles of Textile Finishing By Asim Kumar Roy Choudhury
