The word "contamination" in this context seems weird to me. Contamination seems like a word more suited for spoiled meat than someone's heart or soul. I guess if one's soul is spoiled like meat that would mean it is rotten and useless. There's no turning back to contaminated meat or rotten fruit; hence, the word fits, I guess. On the other hand, I think that words like despondency or disappointment work better. The monster was like a little child losing his hope in humanity once reality set in about how the world would always view him. As for Victor, he went too far and couldn't undo what he had created; then, unfortunately, it totally backfired in his face! Contaminated? I guess there was no going back for him either after he created the monster and avoided responsibility for him. Then to have his fiancee/wife murdered by what he created!? Guilt-city!
As a side note, one could argue that Victor's heart was contaminated by his obsession for reanimating life. As for the creature, in regards to novel ideas about the creature's heart, his heart could have been contaminated by the person who possessed his heart prior to its insertion into his body by Victor. Outside of that, the main controversy is if the creature is/was innately evil or if the lack of nurture forced him to be evil.
Victor's spiritual contamination is evinced in his seething desire to avenge himself upon the creature that he has abandoned to the world. He refuses to create a female companion for the creature without considering the consequences of this action as a murderous one.
One quotation that may be useful to you is this one:
The different accidents of life are not so changeable as the feelings of human nature. I had worked hard for nearly two years, for the sole purpose of infusing life into an inanimate body. For this I had deprived myself of rest and health. I had desired it with an ardour that far exceeded moderation; but now that I had finished, the beauty of the dream vanished, and breathless horror and disgust filled my heart.
If you go to Google and search for "Gutenberg Frankenstein," you will be taken to a text which you can easily search for all references to the word "heart."