I am trying to achieve the CRISPR KNOCK IN of HDR 1.7 kb in HEK293T will one sgRNA will be efficient to get a knock in or else should I use two sgRNAs?
In short, yes! One sgRNA would be sufficient assuming it is a potent sgRNA (high editing frequency). Now with a 1.7 kb insert, the frequency is going to be very low, so it is advisable to include a selection marker (commonly antibiotic or fluorescent marker). Also, you could consider various HDR templates such as single- vs double-stranded, and modified terminal bases vs unmodified template.