[Tex/LaTex] inline citation ‘et al.’ font formatting issues

Question

This is my first question to any StackExchange ever so please bear with me! I am writing my thesis using two fonts, a serif font for the main text and a sans-serif font for the captions for tables and figures. Some of these captions contain in-line citations that have an `et al.' in them – however, instead of following the sans-serif font of the caption, they retain the serif font. A minimum example is shown below (and the code to generate it).

\documentclass{article}

%Temporary Bibliography
\usepackage{filecontents}
\begin{filecontents}{\jobname.bib}
@book{alberts_2008,
  place={New York}, 
  title={Molecular Biology of the Cell}, 
  publisher={Garland Science}, 
  author={Alberts, Bruce and others}, 
  year={2008}
}
\end{filecontents}
\immediate\write18{bibtex \jobname}

%Load packages
\usepackage{booktabs}
\usepackage{fontspec}
\usepackage[colon, authoryear]{natbib}

%Set fonts
\setromanfont{Times New Roman}
\setsansfont{Helvetica}

%Define Caption Options
\usepackage[labelfont={bf,sf,singlespacing},
                textfont={sf,singlespacing},
                justification={justified,RaggedRight},
                singlelinecheck=false,
                margin=0pt]{caption}

\begin{document}
The quick brown fox jumps over the lazy dog \citep{alberts_2008}.

\begin{table}
\caption{Sample data}
\centering
\begin{tabular}{ccc}
Sample & A    & B   \\
One    & 7.5  & 5.5 \\
Two    & 3.45 & 3.4
\end{tabular}
\caption*{

From \citep{alberts_2008}}
\end{table}

%Print Bibliography
\bibliographystyle{cell}
\bibliography{\jobname}
\end{document}

I am open to any type of solution! Also, thanks to the advice of some posters, I have cleaned up this example quite a bit.

Answer 1

In case you are not bound to use bibtex, you could circumvent the problem by using biblatex:

\documentclass{article}

%Temporary Bibliography
\usepackage{filecontents}
\begin{filecontents}{\jobname.bib}
@book{alberts_2008,
  place={New York}, 
  title={Molecular Biology of the Cell}, 
  publisher={Garland Science}, 
  author={Alberts, Bruce and others}, 
  year={2008}
}
\end{filecontents}

\usepackage[natbib=true, style=authoryear, giveninits=true]{biblatex}
\DeclareFieldFormat{title}{#1}
\addbibresource{\jobname.bib}

%Define Caption Options
\usepackage[labelfont={bf,sf,singlespacing},
                textfont={sf,singlespacing},
                justification={justified,RaggedRight},
                singlelinecheck=false,
                margin=0pt]{caption}

\begin{document}
The quick brown fox jumps over the lazy dog \citep{alberts_2008}.

\begin{table}
\caption{Sample data}
\centering
\begin{tabular}{ccc}
Sample & A    & B   \\
One    & 7.5  & 5.5 \\
Two    & 3.45 & 3.4
\end{tabular}
\caption*{From \citep{alberts_2008}}
\end{table}

%%Print Bibliography
\printbibliography
\end{document}