Classical strategies for gene microarrays require labeling of probes or target nucleic acids with signaling molecules, a process that is expensive, time consuming and not always reliable. Bazan and colleagues showed that a nucleic acid-binding cationic conjugated polyelectrolyte can be used in label-free DNA microarrays based on surfaces modified with neutral peptide nucleic acid (PNA) probes. This technique provides a simple and sensitive method for DNA detection without the need for covalent labeling of target DNA.