• Capsule : Which will contain the biological material:
  • protective (passive/active) material
  • schields (radiations, cosmic ray etc...)
  • surviving kit (to warm/cold the biological material)
  • etc.
  • Propulsion systems : depend of the type of caps size/mass etc parameters: 
  • Energy type a) to go on orbit, b) to reach the min speed of 16.6 km/s (to go out of the solar system, the speed is of 42.1 km/s based on the solar referential)
  • time of the journey... here to justify that the first stars are near 270kUA from Earth, depend of the final speed of your capsule
  • Protective systems for landing to insure the biololgicla material will survive to the landing
  • link directly to your design
  • etc.
As discussed, all your calculations must have the "earth value" to developp the bacteria in good conditions. 
For example : if your protective system is previous for a "earth athmospere density" and your seed will touch a "gaz planet..." your seed will be destroyed (by pressure, etc.). You must define which margin are acceptable for your project.
1, Propulsion system 
  • Rocket propulsion just beyond earth orbit (i.e. Hidrogen - Oxygen tanks)
  • Ionic propulstion beyond earth orbit, with slingshot using high gravitational planets in our solar system. I.e. Jupiter / the sun.. etc.. 
  • Nuclear reactor ( or alternative energy source ) to drive the ionic propulsion system
2, Surface penetrator 
2,Guiden system Rocket -- Gravity of sun to leave the solar system ---  Rotating object, 
  • Interitial guidence systems are normally built using gyroscopes. Alternatives to be investigated ( mapping of star locations using photo sensors is one idea that comes to my mind )