No employee of the department shall either directly or indirectly be a party to or be in any manner interested in any contract or agreement with the department for any matter, cause or thing whatsoever by reason whereof any liability or indebtedness shall be in any way created against the department. If any contract or agreement shall be made in violation of the provisions of this section, the same shall be null and void, and no action shall be maintained thereon against the department.
35 P.S. § 755.11