Injectable Polymer

Objectives

To develop and test an injectable polymer that could be used to implant marine animals' tissue to form the basis of a tagging method. The material should have the following properties:

• Non - toxic
• Non - degradable (for at least 2 years)
• Harden into a solidified sphere when injected
• Injected at room temperature or within the range of tolerance of the marine animal

Project Background:

Marine animals can be identified by natural markings, or by applying tags and brands. The tagging of marine animals is important to marine biologists as it provides information on stock identity, movements and migration, abundance, age and growth, mortality and behaviour. By doing so, this would allow a more effective management of fisheries and allow marine biologists to have a better knowledge of the diversity, abundance and distribution of the population as a whole. The emerging interest in polymer science has led to the development of tagging methods which utilise this new technology. This project focuses on the development of a polymer/solvent formulation for the tagging of Abalone.

Experimental

Research and previous works concluded using Polymethylmethacrylate (PMMA) as the polymer. Chloroform, Ethanol and Tetrahydrofuran (THF) as possible solvents were experimented and their concentrations varied. PMMA was first dissolved in the solvent mixture and the resultant polymer mix was injected into various mediums using a hypodermic syringe. The mediums that were used to model the marine animal's body were 0.6 M salt solution, 2% CMC solution and chicken breast.

Results

Figure 1.1 Polymer mix when injected into 2% CMC

Three sets of experiments were carried out, using different solvents in varying combinations and concentrations.

In set 1, it was found that a THF/PMMA solution dispersed in 0.6M salt solution. As such, it was concluded that THF was not a suitable solvent. Experiments with chloroform and ethanol were more successful.

In set 2, chloroform and ethanol mixtures were studied extensively. The most promising results were obtained with 2.5g of PMMA and 1ml each of chloroform and ethanol. This combination resulted in a solid, spherical polymer. All experiments were conducted in a 0.6M salt solution.

In set 3, injection method and injection medium were studied. The solution was injected into 2% CMC solution and chicken breast. Previously, problems had been encountered with the large solids content of the mixture. This was overcome with the use of a larger needle (approximately 1.5mm ID). It was believed that the best injection position was through the Abalone's respiratory holes, through to the animal's gonad.

Conclusions and Recommendations

• The formulation that was developed met 3 of the 4 requirements.
• The polymer can be injected into the animal at room temperature.
• The polymer hardened into a solidified sphere, within 24 hours.
• The polymer is non-degradable for at least two years.
• Final solvent composition was of 50-50vol% Chloroform and Ethanol (1ml each) mixed with 2.5g of PMMA.
• The toxicity of the polymer could not be determined. This will require trials on the Abalone.
• More research work has to be done to ensure that the non-toxic objective is met.