In this paper, an optical sensor design is proposed with low-symmetric photonic crystals that support surface modes. In order to obtain low symmetry, rotational symmetry is broken within the unit cell size while translational symmetry of the photonic crystal is kept intact. In addition, an air slot is embedded on the surface to enhance light interaction with the sample, and the rotational manipulation of the holes' orientation induces surface modes appearing in the bandgap region. The 3D frequency and time-domain calculations are carried out for the proposed structure. The high-sensitivity value of similar to 2100 nm/RIU is achieved with a strong light-matter interaction between the propagating light and the analyte. Different sensitivity values are mapped for different angle values of holes on the surface and different slot widths. Low-symmetric photonic crystal sensor structure is also numerically analyzed for certain refractive index values in terms of biosensor applications.