Is it permissible to purchase a car and pay its installments using a relative's bank investment certificates as collateral, without benefiting from the usurious interest of these certificates?

Investment certificates are an usurious loan. Making them collateral for purchasing a car is a pledge for a debt, which is a matter of scholarly disagreement. However, what prevents this pledge here is that these certificates are forbidden usury, and dealing with them or pledging them is an acknowledgment and encouragement of engaging in usury.