(a) A bank may pledge or otherwise grant security interests in its assets to secure deposits of:

(1) Public funds;

(2) Funds of a pension fund for employees of a public body of the state;

(3) Funds for which a public body of the state or an officer or employee thereof or any court of law is the custodian or trustee pursuant to statute;

(4) Funds held by the department as receiver;

(5) Funds which are required to be secured by law or by an order of a court;

(6) Its own fiduciary funds or the fiduciary funds of an affiliate. In either case, the funds shall be deposited with the pledging institution and held in its commercial department; and

(7) Public funds deposited in another bank.

(b) Except for the deposits listed in subsection (a) of this Code section, a bank may not pledge or otherwise grant security interests in its assets as security for deposits unless otherwise specifically approved in writing by the department.