Preventing HIV/AIDS: using Liquid Silicone Rubber

Preventing HIV/AIDS: using Liquid Silicone Rubber


True that it isn’t much talked about these days as cancer. But the World Health Organisation still bears data that shows about 34 million people around the globe in 2011 managed to breathe air carrying this disease and 1.7 million lost their lives. It is definitely one of the most fatal diseases that has engulfed humanity since it was first detected.


There could be some good news: a relatively recent tool that could help to fight back HIV/AIDS is known to be in the Stage III clinical testing being carried out by the US FDA. It constitutes an anti-viral drug that is mixed in a two-component liquid silicone rubber (LSR) that is injection molded into a vaginal ring that releases the drug.


A highly advanced combining process was customized for this drug. The machine, metering system and mold – all were created to function with a clean room cell that is at par with the ISO 13485 and FDA’s ‘Good Manufacturing Practices’ (GMP) set of guidelines, also exceeding the Six Sigma standards.


This vaginal ring that releases the anti-viral drug is an endeavor of QPharma AB of Malmo, Sweden and happens to be both the OEM as well as the organisation that molds the product.


A to-test production system was constructed by making use of an all electric injection machine from Arburg of Germany the American office of which is in Newington, Connecticut. The LSR metering system was taken from 2KM of Germany and the mold was taken from Austria’s Rico Elastomere.


The grayish white vaginal ring made of LSR is of 8g weight and consists of 25 mg of a microbiocide Dapivirine; also 30% silica in both A and B ingredients.In order to maintain the standard of quality of the particular product, the dosage of the drug must be maintained at a level between 22.5 and 27.5mg. Now, here the most ‘active’ component is a micro-powder that is insoluble in the LSR. QPharma uses a non contact, indestructible Raman spectroscopic analysis of every molded component to make sure that there is a uniform distribution of the HIV/AIDS anti-viral in the ring.


Post the initial stages of testing, it was decided to do away with premixing the drug with a certain silicone oil. This was added initially as a third stream while molding the LSR. The molded ring was left with a lesser concentration of the active component due to the specific component trying to separate from the silicone oil. The optimum results were obtained when the micro-powder was mixed with the silicone oil and then gradually added to the LSR components in equal proportions and then blended in the 2KM metering system. This process had a better stability , was doubly better than the three flow system and the distribution of the drug in the rings was more uniform.


The essential information of the ring is given asunder:


“The vaginal ring has an O.D. of 56 mm and thickness of 7.7 mm. It is molded in 16 cavities at 100 to 200 C. The non-optimized cycle was between 1 and 2 min. Total shot is 125 cm³, injection time is 6.5 sec, and holding pressure is 250 bar (3628 psi)”


The clinical trials showed that the amount or percentage of microbiocide used was definitely not affected by the injection molding procedure. The most important quality determining factors were: shot volume and holding pressure, both very significant for keeping up the I.D of the vaginal ring as well as the correct weight. Part quality was negligibly influenced by parameters like time.


After much research it was found that the product can very well surpass Sig Sigma standards. However, what it can do for prevention of HIV/AIDS is yet to be seen.




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