Question
What is the best gelling agent that can be used for plant tissue culture?
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Most recent answer
Gelling agents are variable and therefore serve broad spectrum, but also best suited to specific applications, dependent on the phenology of the plant, period inoculum stays in the medium, as well as purpose for which you grow the plant or tissue on medium; as such you will need to take these factors into consideration before deliberating on the choice of gelling agent..,
All Answers (17)
Dear Mr Narayanan
There are many gelling agents. Some of the common ones are acacia, alginic acid, bentonite, Carbopols® (now known as carbomers), carboxymethylcellulose. ethylcellulose, gelatin, hydroxyethylcellulose, hydroxypropyl cellulose, magnesium aluminum silicate (Veegum), methylcellulose, poloxamers (Pluronics), polyvinyl alcohol, sodium alginate, tragacanth, and xanthan gum. Though each gelling agent has some unique properties, there are some generalizations that can be made.
1- If the gelling agent is added to the dispersing medium in a haphazard manner, there is a tendency for the agent to "clump." The outer molecules of the gelling agent contact the medium first and hydrate forming a surface layer that is more difficult for the medium to penetrate. The clumps will ultimately hydrate, but it will take more time. A much more efficient manner is to sieve the agents onto the surface of the medium a little at a time as the medium is stirring. Using glycerin as a wetting agent will sometimes minimize clump formation.
2- Some gelling agents are more soluble in cold water than in hot water. Methylcellulose and poloxamers have better solubility in cold water while bentonite, gelatin, and sodium carboxymethylcellulose are more soluble in hot water. Carbomers, tragacanth, and alginic acid gels are made with tepid water.
3- Some gelling agents (carbomers) require a "neutralizer" or a pH adjusting chemical to create the gel after the gelling agent has been wetted in the dispersing medium.
4- Most gelling agents require 24-48 hours to completely hydrate and reach maximum viscosity and clarity.
5- Gelling agents are used in concentrations of 0.5% up to 10% depending on the agent.
6- It is easier to add the active drug before the gel is formed if the drug doesn't interfere with the gel formation.
7- Only Carbopol 934P, methylcellulose, hydroxypropylmethylcellulose, and sodium carboxymethylcellulose are recommended for oral administration.
Carbomer is a generic name for a family of polymers known as Carbopol. Carbopols were first used in the mid 1950s. As a group, they are dry powders with high bulk densities, and form acidic aqueous solutions (pH around 3.0). They thicken at higher pHs (around 5 or 6). They will also swell in aqueous solution of that pH as much as 1000 times their original volume. Their solutions range in viscosity from 0 to 80,000 centipoise (cps).
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1 Recommendation
Dear Mr Narayanan
Some examples of gelling agents are
Polymer Name Viscosity* Properties
Carbopol 910 3,000 - 7,000 Effective in low concentrations and will provide a
low viscosity formulation.
Carbopol 934 30,500 - 39,400 Effective in thick formulations such as emulsions,
suspensions, sustained-release formulations,
transdermals, and topicals. Forms clear gels with water.
Carbopol 934P 29,400 - 39,400 Same properties as 934, but intended for
pharmaceutical formulations.
"P" = highly purified product
Carbopol 940 40,000 - 60,000 Effective in thick formulations, very good clarity
in water or hydroalcoholic topical gels.
Forms clear gels with hydroalcoholic systems.
Carbopol 941 4,000 - 11,000 Produces low viscosity gels, very good clarity.
1 Recommendation
Dear Mr Narayanan
Carbomer polymers are best introduced into water by slowly sprinkling a sieved powder into the vortex created by rapid stirring. This should prevent clumping. Once all of the powder has been added, the stirring speed should be reduced to decrease the possibility of entrapping air bubbles in the formulation.
As mentioned, when the carbomer is dispersed, the solution will have a low pH. A "neutralizer" is added to increase the pH and cause the dispersion to thicken and gel. Some neutralizing agents are sodium hydroxide, potassium hydroxide, and triethanolamine. If the inorganic bases are used to neutralize the solution, a stable water soluble gel is formed. If triethanolamine is used, the gel can tolerate high alcohol concentrations. The viscosity of the gel can be further manipulated by propylene glycol and glycerin (to increase viscosity) or by adding electrolytes (to decrease viscosity).
The cellulose derivatives (methylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, hydroxypropylmethylcellulose, and carboxymethylcellulose) are commonly used. There are some commonalties in these compounds, and each one has their unique properties.
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1 Recommendation
Agar agar is frequently used for solidification of culture media. Other agents like Gelrite, Phytagel, Gellan Gum are also used.
Plant tissue culture takes place in three-dimensional space. Callus cells, singly or in very small clusters, can be grown in liquid media, but for shoots to extend up and then roots to grow down, the callus cells are plated on a semi-solid gel surface. We offer a variety of gelling agents to allow the researcher to optimize the regeneration conditions for each species. The gelling agent of choice may change with the stage of the plant development. Agar is often the first choice to solidify the nutrient culture medium. It is a natural polysaccharide product extracted from red algae seaweed.. We offer agar choices that differ in degree of purity as well as gelling temperature, trace element composition, ash content, and pH. Agarose, the gelling component of agar, may be used in suspension cultures as well as gels. PhytagelTM ,our bacterially produced polysaccharide composed of glucuronic acid, rhamnose, and glucose, is a superior replacement for agar in some cases. Phytagel is clear, colorless, and makes a high strength gel. AgargelTM blends Phytagel with agar. Alginic acid, extracted from brown algae, is used to encapsulate protoplasts.
Gel rite is very good gelling agent as it gives transparency to media so one can study root growth and development. also it requires half the quantity of usual agar as gelling agent
Phytagel is an excellent gelling agent because the media is clear incase of contaminations it is very easy to detect it
