Why is Bassanio so nervous about Antonio signing the loan agreement?

Bassanio is nervous about Antonio signing the loan agreement because he knows that Antonio's financial situation is precarious; he has his wealth tied up in ships that are currently at sea. Additionally, Bassanio feels the weight of responsibility, as he is seeking the loan to court Portia, and he fears that if anything goes wrong with the loan, it could jeopardize both Antonio's safety and their friendship. The potential consequences of defaulting on the loan add to his anxiety, given the harsh terms of Shylock's agreement.