I tried to save my business by mortgaging my home and depositing the money into the business. Even with that capital injection I still ended up closing the company. I lost all that money and am still paying the mortgage back. Can I deduct that investment or loan as a loss on my personal taxes

Yes, if the business was a sole proprietorship. The expenses incurred are reflected on the Schedule C, and the expenses which exceed the gross income are the loss that can be deducted on your tax return.

You can deduct the interest on the mortgage on Schedule A.

You may also be able to deduct it if the business is a S corporation or partnership, but I cannot give you the details on how to deduct the loss.