The present invention relates to novel compositions and methods for potentiating the activity of biologically active molecules in conjunction with one or more delivery vehicles and one or more carrier molecules. Specifically, the invention features the use of a carrier molecule in combination with a delivery vehicle and a biologically active molecule of interest to potentiate the activity of the biologically active molecule. The carrier molecule can be biologically inert, inactive, or attenuated; or can alternately be biologically active in the same or different manner than the biologically active molecule of interest. Specifically, the invention features novel particle forming delivery agents including cationic lipids, microparticles, and nanoparticles that are useful for delivering various biologically active molecules to cells in conjunction with a carrier molecule. The invention also features compositions, and methods of use for the study, diagnosis, and treatment of traits, diseases and conditions that respond to the modulation of gene expression and/or activity in a subject or organism that are delivered intracellularly in conjunction with a carrier molecule. In various embodiments, the invention relates to novel cationic lipids, microparticles, nanoparticles and transfection agents that effectively transfect or deliver biologically active molecules, such as antibodies (e.g., monoclonal, chimeric, humanized etc.), cholesterol, hormones, antivirals, peptides, proteins, chemotherapeutics, small molecules, vitamins, co-factors, nucleosides, nucleotides, oligonucleotides, enzymatic nucleic acids, antisense nucleic acids, triplex forming oligonucleotides, 2,5-A chimeras, allozymes, aptamers, decoys and analogs thereof, and small nucleic acid molecules, such as short interfering nucleic acid (siNA), short interfering RNA (siRNA), double-stranded RNA (dsRNA), micro-RNA (miRNA), and short hairpin RNA (shRNA) molecules, to relevant cells and/or tissues, such as in a subject or organism, in conjunction with one or more carrier molecules. Such novel cationic lipids, microparticles, nanoparticles and transfection agents that are used in conjunction with one or more carrier molecules are useful, for example, in providing compositions to prevent, inhibit, or treat diseases, conditions, or traits in a cell, subject or organism.