This work presents the design and experimental validation of a low-noise amplifier based on a ultra-low-noise JFET for noise characterization of materials samples for neural interfaces. The JFET LNA amplifies the sample noise power by 46 dB well above a lock-in amplifier noise floor, used as spectrum analyzer for noise characterization. The LNA exploits the high gm and low flicker corner frequency of JFETs to achieve 0.15 dB noise figure. The JFET LNA has been characterized in terms of frequency response and noise power spectrum and experimentally validated by characterizing the noise spectrum of a platinum silicide (PtSi) sample.