Bispecific antibodies (bsAbs) have emerged as a class of promising anti-cancer and anti-infection biological drugs. They are capable of killing target cells, either cancer cells or microbe-infected cells, at levels of nanograms per milliliter serum in vivo, about 1e+5 folds more powerful than regular antibodies. To bypass the problems of high cost in production and inconvenience in administration, a logical solution is to use gene therapy vectors to produce them in vivo. In a series of preclinical studies, we have demonstrated that DNA MiniCircle was able to express far above therapeutic levels of bsAB persistently both in the presence as well as the absence of transfection co-factors. As a specific and intended improvement of the claimed invention, an enhanced form of bispecific antibodies incorporating a target cell-effector cell bridging device (BTEC) is additionally disclosed.