**1. Introduction**

Molecular farming is a biotechnological program that includes the genetic modification of agricultural products to produce proteins and chemicals for commercial and pharmaceutical

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purposes. A vast majority of developing countries cannot afford the high costs of medical treatments resulted from the existing methods. Hence, we need to produce not only the new drugs but also the cheaper versions of the present samples in the market. Molecular farming can offer efficient solutions for the current growing need for the biomedicines [1]. Plants provide an inexpensive and simple system for the production of valuable recombinant proteins on large scale, and compared to the other production systems, they have numerous advantages in terms of economy, safety, and applicability. Though using transgenic plants has entailed some sorts of limitations and concerns, the optimization has been operated for solving the existing problems. Normally, the production of pharmaceutical proteins has been largely concentrated by the technology of molecular farming in plants, also plants can be used for the production of food supplements, biopolymers, industrial enzymes, and proteins in the investigations (avidin, β-glucuronidase, etc.). Prior production systems, including bacteria, microbial eukaryotes (yeasts, double-stranded fungi), animal cells, and transgenic animals, as a result of their limitations, were replaced by transgenic plants. The primary recombinant pharmaceutical proteins, extracted from the plants (hormones of human growth), and the first recombinant antibodies were generated from transgenic plants, respectively, in 1986 and 1989 [2, 3]. In 1997, the first recombinant protein, avidin (egg protein) was produced in a transgenic maize for industrial uses [4]. These applications proved that plants can be converted into bioreactors to produce a wide range of recombinant proteins. Many years had already passed when it was proved that plants were even able to produce several complexes of functional mammal proteins with the pharmacological functions, such as human serum proteins, growth regulators, antibodies, vaccines, hormones, cytokines, and enzymes [5]. An increasing request for the biomedicines was aligned with the high costs and inefficiency of existing production systems [6] including yeasts, bacteria, animal cells [7], and transgenic animals [8].

The aim of this study is to review the technologies of molecular farming, limitations and advantages of plant systems, challenges, bio-security, public acceptance of molecular farming.
