**4.3.2. Surface modification via capsid display, chemical coupling or electrostatic interactions**

Other than the display on the envelope, heterologous protein has been displayed on the capsid by fusion with the major capsid protein VP39. The VP39 fusion with enhanced green fluores‐ cent protein (eGFP) neither interferes with the virus assembly nor affects the virus titer, thereby enabling intracellular baculovirus trafficking and biodistribution monitoring [114]. Similarly, the ZnO binding peptide has been fused to the N‐terminus of VP39 while retaining the viral infectivity and conferring the ability to bind nanosized ZnO powders [115]. Besides, by fusing the protein transduction domain (PTD) of human immunodeficiency virus (HIV) TAT protein (a protein responsible for nuclear import of HIV genome) with VP39, the engineered baculo‐ virus results in improved transduction of various mammalian cells

Baculovirus can also be chemically conjugated with compounds such as polyethylene glycol (PEG) alone and folate [116] to improve the transduction of folate receptor‐positive KB cells. Additionally, baculoviral vectors have been coated with positively charged polyethylenimine (25 kDa) through electrostatic interactions. The modification imparts baculoviral vectors resistance to human and rat serum‐mediated inactivation in vitro and elevates in vivo transduction in the liver and spleen after tail vein injection into mice.
