The Atrigel® system is a sustained-release drug delivery platform that delivers a wide spectrum of drugs over a few days to several months with a single injection. Atrigel® consists of biodegradable polymers dissolved in biocompatible carriers. When the liquid product is injected into the subcutaneous space through a small gauge needle, water in the tissue fluids causes the polymer to precipitate and trap the drug in a solid implant. A number of marketed products based on this technology include Atridox® and Atrisorb (Doxycycline hyclate), Eligard (Leuprolide acetate), Sandostatin® (Octreotide acetate), and Sublocade® (Buprenorphine extended-release) etc. 

a) Explain how the sustain-release of incorporated drug can be achieved. (5 marks) 

b) Drug delivered by the Atrigel system can last for a few days to several months. Please list out THREE factors that can affect the release rate and provide brief explanation. (6 marks) 

c) Please comment on the ADVANTAGE and DISADVANTAGE of Atrigel® drug delivery system. (4 marks)