Here are a few suggestions about where to stay in Vienna close to the Vienna BioCenter or well connected to it by public transport. It goes from more expensive to cheaper possibilities.
Hotel Savoyen (**** Superior): This traditional, but modern hotel is located half way between the Vienna BioCenter and the inner city. It is only three tram stops away with tram 71 from the conference location. https://www.austria-trend.at/de/hotels/savoyen
Hotel Doppio (****): It is a classical conference hotel and it is in close walking distance (5 minutes) from the Vienna BioCenter. It takes about 15 to 20 minutes to go to the inner city with tram 71. http://www.austria-trend.at/Hotel-Doppio/en/
Hotel Daniel (****): This trendy hotel is located close to Wien Hauptbahnhof (main station) and three tram stops away from the conference location. http://www.hoteldaniel.com/en/vienna/
Mercure Grand Hotel Biedermeier Wien (****): This classical, Viennese hotel is in walking distance to the city center (15 minutes walk to St. Stephen’s cathedral), but nevertheless only 6 bus stops away from the conference location. Take bus 74A to Viehmarktgasse, which is right around the corner of Vienna BioCenter. http://mercure-grand-biedermeier-hotel-vienna.hotel-ds.com/de/
Hotel Gabriel (***): This standard hotel is the closest one to the conference location, it is only a 3 minutes walk away. The bus 74A stops right in front of the hotel and it takes 15 minutes to go to the city center. http://www.adler-hotels-wien.at/en/gartenhotel-gabriel/home/index.html
These are only a few options, which are all located in close vicinity of the conference location. In Vienna, there a hundreds of possibilities- from cheap to expensive- of where to stay so feel free to book an accommodation of your choice.