Sensing and amplifying weak signals are critical for life things to adapt to the severe environment. These sensing and signal transduction systems have been highly developed to play the role in the course of evolution. For example, we can raise immune and neurotransmission systems. These systems work very effectively, however application usages of those are limited because they only work in living cells. Sensing and signal transduction systems made of purified biomolecules and/or chemicals will overcome the situation.
Motivation Signal transduction with defined biomolecules and chemicals needs two system; sensing systems to external signals and transmit systems to amplify the signals. Liposomes have high responsibility to environment and have been used to release molecules out from the inside. DNA is beneficial for specific-action and transmission, because of its high selective-specificity and flexibility. If above system is made of DNA and liposomes, we can realize the nano-scaled flexible amplifier. Thus, we aim at creating molecular-releasing systems using DNA and liposomes.

Project: Lipo-HANABI

As our summer project, we decided to construt a signal amplification system by using Liposomes and DNA nanotechnology. The system has two stages: "Initiation by senseing environment" and "Amplification of signals by chain-reactive burst of liposomes".

First stage : Initiation by senseing environment

The first stage senses environmental changes, and release secondary signals into the amplifier in the sexcond stage. In this project, we chose temperature as an environmental initiator because of controllability. Increasing temperature induces disruption of initial liposomes. Key DNA inside the liposomes is released and transmit signals into the second-stage amplifier

Second stage: Amplification by chain-reactive burst of liposomes
The second stage recieve the signals from the first stage, and then amplify them by a chain reactive liposome destruction. The liposomes in the second stage encapsulate key DNAs and payload moleclules (like drugs). Once a liposome is disrupted, neighbor liposomes are also disrputed by the key DNA. This happens continuously, and then, the number of disrupted liposomes increases exponentially. Since the second-stage liposome also encapsulate payload molecules as a response to signals, the response initiated by the first signals is amplified in this stage.

The advantage of the two-stage strategy is that we can make various types of signal amplification system without changing the 2nd stage.

This system works like a HANABI (Japanese fireworks), because HANABI is resulted from chain-reactive bursts initiated by fire (first signal). Thus, we termed the project as "Lipo-HANABI" (we should note Lipo means liposomes).