When using biblatex, most citation styles do not retain capitalization of titles. This little R script reads in an existing bib file, changes the titles and then saves another bib file.

change_bib_retain_capitalizationtitle.R

# read in the initial bib file
tex <- readLines("test.bib")

# get the location of the titles (NOTE: also will include fields of the nature 'booktitle')
title_loc <- grepl("title", tex, fixed = TRUE)

# Change the opening bracket from { to {{
# the full regex looks for strings containing 'title = {,' or 'title={' and replaces it with 'title = {'
tex[title_loc] <- gsub("title = \\{|title=\\{","title = {{",tex[title_loc])

# Change the closing bracket from } to }}
# the full regex looks for strings ending '},' or '} ,' and replaces it with '}},'
tex[title_loc] <- gsub("\\},$|\\} ,$","}},",tex[title_loc])

# show result
tex

# write out the final adjusted file
writeLines(tex, con = "test1.bib")