You're still not very clear, but presuming the inputs are referenced to ground, and not floating, you can't multiplex then as a matrix. You also don't give any clue if they are analogue or digital either - in fact you don't give much info at all. But if it's analogue look at CMOS switches, if it's digital, then decoder IC's.
If all inputs are to be read, and not used for interupts AND digital, then some parallel to serial shift registers, cascaded would do. Of course, its a bit of a hassle to check their status, as you'd have to read them in all at once, or at least one cihp at a time (8-bits).
Or you could do it in parallel, using D-type latches, and tristate outputs.