The ornamental design for a bio-sensor, as shown and described.
FIG. 1 is a front view of a bio-sensor of a new design;
FIG. 2 is a back view thereof;
FIG. 3 is a left side view thereof;
FIG. 4 is a right side view thereof;
FIG. 5 is a plan view thereof;
FIG. 6 is a bottom view thereof; and,
FIG. 7 is an assembling view showing a condition wherein the bio-sensor is incorporated in a sensing apparatus.
The broken line showing of structural features are included for the purpose of illustrating non-claimed subject matter and forms no part of the claimed design.