BackgroundFor all living organisms, sensing weak signals in environment and amplifying them are critically important to survive. Various types of signal sensing/ transduction systems have been highly developed in the course of evolution, e.g. immune and neuro-transmission systems. These systems are not only astonishingly sensitive but very effective and efficient. If we could borrow principles from the living systems, we could create a system with novel functionalities. In our project, we decided to create a sensing and signal transduction systems made of designed artificial biomolecules and chemicals.
MotivationIn order to realize a signal transduction system, we need to develop two types of system; a sensing system that detects external signal and a transmitting system that amplifies the signal and releases large amount of output molecules (payloard). We adopt liposomes as a container of the system.
Project: Lipo-HANABIIn our system, stored molecules in liposome are released in chain-reaction triggered by environmental stimuli. The system adopts a two-stage mechanism as follows.
1st stage: Sensing systemThe 1st stage detects a certain signal in the environment, and release molecules to activate the 2nd stage. In this project, we chose temperature change as an environmental signal that initiates the whole process. Namely, we use a temperature-sensitive liposome for the 1st stage. At a certain triggering temperature, they break and release key molecules for the 2nd stage. The released key molecules attach on the 2nd stage liposomes and induce puncture of them.
2nd stage: Amplification systemThe 2nd stage liposomes contain both the payload molecules (e.g. drug) and the same key molecules received from 1st stage. Once some of them break, it releases more key molecules, and they break other liposomes in their neighborhood. As a consequence, bursting of the liposomes propagates exponentially in a chain-reactive way and releases a lot of payload molecules The advantage of adopting the two-stage strategy is that we can develop various types of signal amplification system by designing the 1st stage, without changing the 2nd stage.
The mechanism of this system is similar to that of HANABI (fireworks in Japanese), therefore, we termed the project "Lipo-HANABI".