The present invention relates to compositions and methods for treating infectious diseases and genetic disorders through gene therapy and intracellular delivery of antisense oligonucleotides or other nucleic acid sequences. In particular, compositions and methods using biologically active nononic reverse block copolymers are described. The reverse copolymers have an inner core of polyoxyethylene (POE) that is flanked on either end by polyoxpropylene (POP). The reverse block copolymers have the following formula: ##STR1##

wherein "b" represents a number such that the molecular weight of the hydrophobe (C₃H₆O)_b is between approximately 750 and 20,000 Daltons and "a" represents a number such that the percentage of hydrophile (C₂H₄O)_a is between approximately 1% and 90% of the weight of the block copolymer.