Is it professionally acceptable to send a follow-up email to make sure my portfolio has been properly looked at?

It surely isn't unacceptable, but it may be unnecessary. It could even be seen as too insistent or desperate for your part if you send that email.

All recruitment processes take some time, how much greatly depending on every company. It is unlikely they forget to review applications they receive or obtain; if they don't contact you it is more likely that they thought you were not a good fit for the job.

However, I would not rush into any conclusions, and give them more time to respond before you can tell for sure.

In the meantime I suggest you keep your options open and try to look for other jobs you may like elsewhere.

Is it professionally acceptable to send a follow-up email to make sure my portfolio has been properly looked at?

It surely isn't unacceptable, but it may be unnecessary. It could even be seen as too insistent or desperate for your part if you send that email.

All recruitment processes take some time, how much greatly depending on every company. It is unlikely they forget to review applications they receive or obtain; if they don't contact you it is more likely that they thought you were not a good fit for the job.

However, I would not rush into any conclusions, and give them more time to respond before you can tell for sure (it has only been 3 days, wait at least a week).

In the meantime I suggest you keep your options open and try to look for other jobs you may like elsewhere.