What tells you it will worth 4 ETH? I see NFTs to benefit the well known people that are very rich in the world just like the art works. You may set the price to 0.4 ETH but that does not mean it is worth the price until you see a buyer for it at the price.
I have not seen anyone that accept NFT offer as a loan collateral on this forum. The chance of you see anything that will accept the offer on this forum is very low. But if you do that, you are doing nothing wrong.
The floor price on
OpenSea is around 4.9 ETH currently.
You can use whatever collateral someone is willing to accept. The liquidity for NFTs is not that great, so you might have to settle for a loan valued significantly lower than your NFT. Even though there are not many sales, there are still people buying NFTs from this collection for thousands of dollars, so there might be somebody willing to offer you a loan.