Fabrication of a Biomimetic Nano-Matrix with Janus Base Nanotubes and Fibronectin for Stem Cell Adhesion

Summary

The goal of this protocol is to show the assembly of a biomimetic nanomatrix (NM) with Janus base nanotubes (JBNTs) and fibronectin (FN). When co-cultured with human mesenchymal stem cells (hMSCs), the NMs exhibit excellent bioactivity in encouraging hMSCs adhesion.

Abstract

A biomimetic NM was developed to serve as a tissue-engineering biological scaffold, which can enhance stem cell anchorage. The biomimetic NM is formed from JBNTs and FN through self-assembly in an aqueous solution. JBNTs measure 200-300 µm in length with inner hydrophobic hollow channels and outer hydrophilic surfaces. JBNTs are positively charged and FNs are negatively charged. Therefore, when injected into a neutral aqueous solution, they are bonded together via noncovalent bonding to form the NM bundles. The self-assembly process is completed within a few seconds without any chemical initiators, heat source, or UV light. When the pH of the NM solution is lower than the isoelectric point of FNs (pI 5.5-6.0), the NM bundles will self-release due to the presence of positively charged FN.

NM is known to mimic the extracellular matrix (ECM) morphologically and hence, can be used as an injectable scaffold, which provides an excellent platform to enhance hMSC adhesion. Cell density analysis and fluorescence imaging experiments indicated that the NMs significantly increased the anchorage of hMSCs compared to the negative control.

Introduction

Human mesenchymal stem cells (hMSCs) have shown the potential for self-renewal and self-differentiation along different mesenchymal lineages, which helps in the regeneration and maintenance of tissues¹. Based on the differentiation potential, hMSCs are considered as candidates for mesenchymal tissue injuries and hematopoietic disorder therapy². hMSCs have shown the ability to promote wound healing by increasing tissue repair, angiogenesis, and reducing inflammation³. However, without biochemical or biomaterials assistance, the efficiency for the hMSCs to reach a target tissue and function at the d....

Protocol

1. Synthesis of JBNTs

NOTE: JBNT monomer was prepared as published previously¹¹.

1. Synthesis of compound A1
   1. Prepare a solution containing 8.50 g of 2-cyanoacetic acid and 9.80 g of ethylcarbamate in 25 mL of toluene and 2.5 mL of N, N-dimethylformamide. Add 4.90 mL of phosphoryl chloride dropwise. Then heat the mixture to 70 °C and keep stirring for 1.5 h.
   2. Cool the reaction mixture to room temperature and pour in 100 g of ice water. Extract the aqueous layer with ethyl acetate (3 x 250 mL), and wash with 100 mL of brine. Dry the organic layer over anhydrous sodium sulfate, filter....

Results

Our studies discovered that the formation of the NM of JBNTs and FN is fast, which happened in 10 seconds. As shown in Figure 2, white floccule was obtained when the JBNT solution was mixed with the FN solution and pipetted several times. The formation process of NM is completely biomimetic. No external stimuli are needed. The process of fabrication is much easier than that of some emerging biomaterials, which is based on ultraviolet light or chemical initiator for crosslinking

Discussion

In this study, we developed a self-assembled biomimetic NM, which was formed with DNA-inspired JBNTs and FN. When preparing the JBNT solution, the JBNT lyophilized powder should be dissolved into the water instead of PBS because PBS will cause agglomeration of JBNTs, which inhibits their assembly. Moreover, the NM should also be assembled in water if we want to observe the nano-fibril structures of the NM, because the salt in PBS will bundle with NM fibers, which can greatly reduce the resolution of the images.

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
1,2-dichloroethane	Alfa Aesar	39121
2-cyanoacetic acid	Sigma-Aldrich	C88505
4-Dimethylaminopyridine	TCI America	D1450
8 wells Chambered Coverglass	Thermo Fisher	155409
96-well plate	Corning	353072
absolute ethanol	Thermo Fisher	BP2818500
acetone	Sigma-Aldrich	179124
acetonitrile	Sigma-Aldrich	34851
allylamine	Sigma-Aldrich	145831
Basic Plasma Cleaner	Harrick Plasma	PDC32G
citric acid	Sigma-Aldrich	251275
concentrated hydrochloric acid	Sigma-Aldrich	H1758
Deionized water	Thermo Fisher	15230147
dichloromethane	Sigma-Aldrich	270997
diethyl ether	Sigma-Aldrich	296082
Di-tert-butyl dicarbonate	Sigma-Aldrich	361941
ethyl acetate	Sigma-Aldrich	319902
ethylcarbamate	Sigma-Aldrich	U2500
Fibronectin	Thermo Fisher	PHE0023
Fixative Solution (4 % formaldehyde prepared in PBS)	Thermo Fisher	R37814
guanidinium hydrochloride	Alfa Aesar	A13543
hexanes	Sigma-Aldrich	227064
Human mesenchymal stem cells	Lonza	PT-2501
methanol	Sigma-Aldrich	34860
methyl iodide	Sigma-Aldrich	289566
N,N-Diisopropylethylamine	Alfa Aesar	A17114
N,N-dimethylformamide	Sigma-Aldrich	227056
N-Methylmorpholine N-oxide	Alfa Aesar	A19802
Osmium tetraoxide	Alfa Aesar	45385
Penicillin-Streptomycin	Thermo Fisher	15140163
Phosphate Buffer Solution	Thermo Fisher	20012050
phosphoryl chloride	Sigma-Aldrich	201170
potassium carbonate	Sigma-Aldrich	347825
reverse phase column	Thermo Fisher	25305-154630
Rhodamine Phalloidin	Thermo Fisher	R415
silica gel	TCI America	S0821
sodium bicarbonate	Sigma-Aldrich	S6014
sodium ethoxide	Alfa Aesar	L13083
sodium periodide	Sigma-Aldrich	71859
sodium sulfate	Sigma-Aldrich	239313
sodium sulfite	Sigma-Aldrich	S0505
sodium triacetoxyborohydride	Alfa Aesar	B22060
spectrophotometer(NanoDrop One/Onec UV-Vis)	Thermo Fisher	ND-ONE-W
Stem Cell Growth Medium BulletKit	Lonza	PT-3001
tetrahydrofuran	Sigma-Aldrich	401757
thioanisole	Sigma-Aldrich	T28002
toluene	Sigma-Aldrich	179418
triethylamine	Alfa Aesar	A12646
trifluoroacetic acid	Alfa Aesar	A12198
Triton X-100	Thermo Fisher	HFH10
Trypsin-EDTA solution	Thermo Fisher	25200056