Induction of Hydroxyapatite Particles Formation on PEGDA-Based Hydrogels by Nanobacteria

Nanobacteria is a tiny structure with size varying 80 to 500nm, commonly occurring in clusters and producing a biofilm which contains carbonate or hydroxyl apatite. In this study, the bioactive synthetic hydrogel materials were prepared with polyethylene glycol diacrylate (PEGDA) and 2-hydroxyethyl mathacrylate (HEMA) by UV photo-polymerization. Bone marrow mesenchymal stem cells (BMSCs) were seeded onto hydrogel surface for five days. The BMSCs cell adhesion on hydrogels was confirmed by SEM to evaluate the biocompatibility of the materials. It was found groups of nanoparticles on the hydrogel surface and the particles were analyzed by SEM. The particles were analyzed for its inorganic chemical constituents using energy dispersive X-ray microanalysis (EDS). The predominant components were found to be calcium (24.40%) and phosphorus (13.98%). The most likely source of cell culture contamination by such organisms is bovine serum albumin (BSA) used as supplement in culture media. Nanobacteria in BSA may be the important factor which accelerated hydroxyapatite crystal growth on hydrogels. It is important to study the biomineralization in biological system and has potential application in biomaterials science and biotechnology.

Henrietta Lacks, HeLa Cells, and Cell Culture Contamination

Henrietta Lacks died in 1951 of an aggressive adenocarcinoma of the cervix. A tissue biopsy obtained for diagnostic evaluation yielded additional tissue for Dr George O. Gey's tissue culture laboratory at Johns Hopkins (Baltimore, Maryland). The cancer cells, now called HeLa cells, grew rapidly in cell culture and became the first human cell line. HeLa cells were used by researchers around the world. However, 20 years after Henrietta Lacks' death, mounting evidence suggested that HeLa cells contaminated and overgrew other cell lines. Cultures, supposedly of tissues such as breast cancer or mouse, proved to be HeLa cells. We describe the history behind the development of HeLa cells, including the first published description of Ms Lacks' autopsy, and the cell culture contamination that resulted. The debate over cell culture contamination began in the 1970s and was not harmonious. Ultimately, the problem was not resolved and it continues today. Finally, we discuss the philosophical implications of the immortal HeLa cell line.

A solution to the generalized birthday problem with application to allozyme screening for cell culture contamination

This paper gives the probability that no common allozyme signature is found among n randomly selected cell culture lines when the s mutually exclusive and exhaustive signatures have arbitrary known probabilities. This result is useful in detecting cell culture contamination by a single cell line. This problem is a generalization of the classic problem of finding the probability of no common birthday among n individuals when it is assumed that each individual has a chance 1/s = 1/365 of a birthday on a given day. Both an exact recursive solution and an approximate solution are given for the general problem.