  We report on some properties of the newly observed charged hidden-charmed
open strange $ Z_{cs}(3985)^- $ state by BESIII Collaboration. Assigning the
quantum numbers $ J^{P} = 1^{+}$ and the quark composition $ c \bar c s\bar u $
and considering it as the strange partner of the famous $ Z_c(3900) $ state, we
estimate the mass of the $ Z_{cs}(3985)^- $ resonance in vacuum and compare it
with the experimental data. We also investigate its mass, current coupling and
vector-self energy in a medium with finite density. Our result on the mass in
vacuum agrees well with the experimental data. We estimate the mass and current
coupling of the b-partner of this state, $ Z_{bs}$, in the vacuum as well. For
its mass we get $ m_{Z_{bs}}= 10732^{+97}_{-46}~\mbox{MeV}$, which may be
checked via other nonperturbative approaches as well as future experiments. We
present the dependence of the spectroscopic parameters of $ Z_{cs}(3985)^- $
state on density and observe that these parameters are linearly changed with
increasing in the density.
