Use of paper as support material for material applications

Introduction: For the past several decades, the paper has been employed as a platform to record and preserve information. Since past few decades, the paper found its use in various biomedical applications. Both µPADs and paper-based scaffolds have shown immense potential to be used as a sensor as well as a supporting material for in vitro tissue engineering. The paper-based microfluidic devices namely the µPADs consist of sample loading and testing zones with varying channel design as per the application requirement. The paper is revolutionizing the field of tissue engineering with the development of paper-based cultures and scaffolds. The review discusses the applications of paper as supporting material in biomedical sciences; both as a diagnosing device and scaffolding material. It aims to encourage similar research in the field and the development of commercially viable paper-based devices in near future. Further, the importance of low-cost paper-based analytical devices and scaffolds is demonstrated. Methods: Earlier tests performed on cell cultures were developed on Petri dishes and glass plates in form of 2D monolayers, but they had major limitations as cell microenvironments were 3D. Hence, researchers started making 3D substrates by employing artificial polymers initially, but they were non-biodegradable and difficult to fabricate. The focus shifted to potential paper based-materials, substrates, and synthetic polymers to make scaffolds. Since the fabrication of these scaffolds was not feasible, but now research is ongoing to replace them with paper-based scaffolds which are low-cost and can mimic the biological Extra-Cellular-Matrix (ECM). This paper-based scaffold can provide a valuable platform for basic stem cell-based research to study material effects and perform drug tests. The fibrous nature, porosity, and flexibility of scaffolds are desirable properties for tissue engineering material and paper have the potential to replace conventional scaffolding materials such as polydimethylsiloxane (PDMS), glass fiber, chitosan, which are difficult to fabricate and are not feasible for low-income economies. Results & Discussions:  For the proper in-vitro proliferation of the cells, a microenvironment that mimics the in-vivo characteristics of the body is crucial. The major challenge with paper is that it is 2D in structure, hence researchers stacked the cell-laden papers on top of one another to make the 3D microenvironments. Using this technique, researchers developed "a beating heart on paper", which worked for about 3 months; they developed a 3D liver model on the paper scaffold which showed response to an actual liver in vivo. Similar to µPADs, the paper substrate used in the fabrication of cultures and scaffolds were surface modified to enhance cellular growth. Conclusions:  The paper-based devices are employed as analytical devices to detect different biomarkers such as viral proteins, metabolites, oncogenes, and antigens. On the other hand, the paper has employed to develop paper-based 3D cultures and scaffolds for the testing of drugs, monitoring their cytotoxic effects and in vitro cell microenvironments. Moreover, these scaffolds are being developed to be used as implantable tissues. Besides the various utilities of paper as supporting material in biomedical sciences; both as a diagnosing device and scaffolding material, it supports clean and sustainable environmental conditions. Keywords: Scaffold, Extra-Cellular-Matrix, µPADs, material Acknowledgment: The author acknowledges the support of online resources and library facilities at the host University in preparation of this article. References Deka B., Bhatia D., Kalita R., Mishra A. Applications of Paper as a support material in biomedical sciences: A Decadal review. Sensors International, Elsevier, 2020; 100004 (1): 1-13. Wang , Li; Xu, Cong; Zhu, Yujuan; Yu, Yue; Sun, Ning; Zhang, Xiaoqing ; Feng, Ke; Qin, Jianhua. Human-induced pluripotent stem cell-derived beating cardiac tissues on paper. Lab On a Chip, 2015; 15(22); 4283-89.