Accordingly, polyelectrolyte films, terminated either with negatively charged HP, referred to as “(PDADMAC/HP)4”, or with positively charged PDADMAC referred to as “(PDADMAC/HP)3/PDADMAC”, were used as effective carriers of the BDNF in a proliferation-limiting system for neuroblastoma cancer cells (referred to as “(PDADMAC/HP)4/BDNF” and “(PDADMAC/HP)3/PDADMAC/BDNF”, respectively). The gene discussed is BDNF; the disease is neuroblastoma.