Is money earned from working with a university degree, the studies for which were financed by an interest-based loan, considered permissible?

Usury is one of the gravest major sins, and it is impermissible to engage in it except in cases of extreme necessity. University studies do not fall under this category, so you must repent for what you have done. As for working with a university degree, there is no impediment to it, as obtaining it through an interest-bearing loan is a separate sin that does not affect the permissibility of working with the degree.