Fibril matrices created with collagen from the marine fish barramundi for use in conventional three-dimensional cell culture.

Collagen obtained from fish offal (skin, scales, and bones) is required from some religious and ethnic groups, thus indirectly increasing demands for fish collagen for biomedical applications. The limitation of fish collagen is its lower thermal stability compared to mammalian collagen. In this study, we focused on collagen extracted from scales of the marine fish barramundi (Lates calcarifer) and demonstrated the suitability for the collagen to be utilized in collagen fibril matrices (CFM). Collagen was extracted from the scales through pepsin-digestion and purified (designated as "BC"). The denaturation temperature (Td) for BC was determined to be 36.4 °C, one of the highest among fish collagens. BC formed CFM which was thermally stable at 37 °C, while Td was lower than 37 °C. This could be explained by the fast fibril formation, initiating at temperatures near 20 °C in a temperature-elevated process. As a result, the NIH3T3 cells were successfully encapsulated in the CFM of BC and cultured three-dimensionally for 7 d. The cells spread and exhibited well-developed pseudopodia in the CFM of BC as observed in the CFM of pig collagen matrices. This is the first report on fish CFM used for conventional 3-D cell culture.

The effect of alkaline pretreatment on the biochemical characteristics and fibril-forming abilities of types I and II collagen extracted from bester sturgeon by-products.

Non-mammalian collagens have attracted increasing attention for industrial and biomedical use. We have therefore evaluated extraction conditions and the biochemical properties of collagens from aquacultured sturgeon. Pepsin-soluble type I and type II collagen were respectively extracted from the skin and notochord of bester sturgeon by-products, with yields of 63.9 ±â€¯0.19% and 35.5 ±â€¯0.68%. Collagen extraction efficiency was improved by an alkaline pretreatment of the skin and notochord (fewer extraction cycles were required), but the final yields decreased to 56.2 ±â€¯0.84% for type I and 31.8 ±â€¯1.13% for type II. Alkaline pretreatment did not affect the thermal stability or triple-helical structure of both types of collagen. Types I and II collagen formed re-assembled fibril structures in vitro, under different conditions. Alkaline pretreatment slowed down the formation of type I collagen fibrils and specifically inhibited the formation of thick fibril-bundle structures. In contrast, alkaline pretreatment did not change type II collagen fibril formation. In conclusion, alkaline pretreatment of sturgeon skin and notochord is an effective method to accelerate collagen extraction process of types I and II collagen without changing their biochemical properties. However, it decreases the yield of both collagens and specifically changes the fibril-forming ability of type I collagen.

A novel method for continuous formation of cord-like collagen gels to fabricate durable fibers in which collagen fibrils are longitudinally aligned.

We developed a continuous formation method of cord-like collagen gels comprising fibrils preferentially aligned along the geometrical axes (CCGs). Collagen (2.5%) dissolved in a sodium phosphate buffer containing 280 mM of sodium chloride was introduced into a stainless cylinder (length 52 mm, diameter 2.0 mm) warmed at 38°C at a linear velocity of 2.5 mm/s. This process caused collagen fibril alignments under acute fibril formation in the cylinder, resulting in continuous formation of CCGs. Fibril formation rate, shear rate, and shear duration were substantial factors for successful CCG formation. Outstanding advantages of this method over conventional wet spinning include the capacity of this technique to form aligned fibrils in the entire gels and to control the diameter of cord-like gels over 1 mm. The air-drying of CCGs which were crosslinked with 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide and N-hydroxy-succinimide produced dry collagen fibers with cross-sectional areas of 0.0123-0.135 mm2 . Upon the rewetting of the fibers, they failed at a stress of 54.5 ± 7.8 MPa, which is higher than the mean failure stress of anterior cruciate ligament tissue (13.3-37.8 MPa). These findings indicate that the CCG formation method enables the fabrication of collagen fibers which are potential components of collagen-based artificial tendons. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B: 1011-1023, 2019.

A novel fabrication method to create a thick collagen bundle composed of uniaxially aligned fibrils: an essential technology for the development of artificial tendon/ligament matrices.

In this study, we developed a fabrication method for thick collagen gel bundles comprising uniaxially aligned fibrils of sufficient size for filling defects in ligament tissues. The fabrication involved rotary shearing to dense collagen sols using a rheometer and then warming them from 23°C to 37°C to trigger gelation upon rotation. Gelation due to collagen fibril formation was accelerated by increased concentrations of neutral phosphate buffer, and fibril alignment occurred within 20 s during the early stage of rapid gelation. Fabrication of gels was completed with slippage between gels and the movable upper plate, and well-aligned fibrils along the rotation direction were observed in the marginal regions of disc-shaped gels. Gel thickness could be increased from 1 to 3 mm with homogeneous alignment of fibrils in the entire sample. The alignment of fibrils improved mechanical properties against tensile loads that were placed parallel to the alignment axis. Elongation of cultured fibroblast along the alignment was observed on the gels. The present method will enable the bottom-up fabrication of an artificial tendon for ligament reconstruction and repair.

Development of a non-blurring, dual-imaging tissue marker for gastrointestinal tumor localization.

BACKGROUND: Knowing the exact location of gastrointestinal tumors both preoperatively and intraoperatively is essential for planning and performing laparoscopic surgery. Different techniques have been introduced to ascertain tumor locations during surgery, but none of these are fully satisfactory at establishing the minimum margins for organ resection while retaining curability. A new, non-blurring tissue marker, detectable by both X-ray computed tomography (CT) and near-infrared (NIR) fluorescence laparoscopy, has been developed, and we here examine its utility using an animal model. METHODS: Liposomes, comprised phospholipids and an NIR fluorescent dye (an indocyanine green derivative), and emulsions, consisting of phospholipids and oily radiographic contrast medium, were combined with polyglycerol-polyricinoleate to form giant cluster-like vesicles. This vesicular dispersion (300 µl) was administered into the porcine gastric submucosa using a gastroendoscope, and the detectability of the marker was examined using X-ray CT and NIR fluorescence laparoscopy. RESULTS: One hour after the administration of the vesicular dispersion, X-ray CT identified four individual injection sites, each at a 1-cm radius of a metal hemostasis clip. NIR fluorescence laparoscopy detected individual fluorescent spots 18 hours after the administration of the vesicular dispersion. CONCLUSION: We anticipate that this newly developed tissue marker will contribute to the preoperative simulation of laparoscopic gastrointestinal cancer surgery and its intraoperative navigation.

Application of a novel near infrared-fluorescence giant vesicle- and polymerasome-based tissue marker for endoscopic and laparoscopic navigation.

In this study, we describe the development of a novel tissue marker that can be injected from within the digestive tract by using an endoscopic instrument, and visualized using near-infrared (NIR) fluorescence imaging. The marker was prepared in three steps, (i) mixing NIR-fluorescent indocyanine green (ICG) with giant vesicles (GVs) of lecithin, (ii) suspending the ICG-containing giant vesicles (ICG-GV) in an oil phase dissolving polyglycerol-polyricinoleate (PGPR), and (iii) centrifugation of the suspension layered on a buffered solution to obtain a giant polymer vesicle (polymerasome) containing ICG-GV. We injected the tissue marker into the inner gastric surface of an anesthetized pig using an endoscopic syringe, and observed the injection site using a fluorescence laparoscopic camera. The diameter of the spot blur was approximately 2 cm over a 5-h period, demonstrating the utility of this procedure as a tissue marker for tumor marking, and suggesting its potential for assisting navigation during surgical procedures.

Evaluation of gelatin hydrogel as a potential carrier for cell transportation.

We prepared uncleaved gelatin composed mainly of collagen α-, ß-, and γ-chains. Gelation and melting of uncleaved gelatin occurred rapidly with moderate decrease and increase in temperature (23°C-37°C). The viability of cells encapsulated in the gelatin gel was greater than 96% after 7 d at 23°C.

Temperature-responsive gelation of type I collagen solutions involving fibril formation and genipin crosslinking as a potential injectable hydrogel.

We investigated the temperature-responsive gelation of collagen/genipin solutions using pepsin-solubilized collagen (PSC) and acid-solubilized collagen (ASC) as substrates. Gelation occurred in the PSC/genipin solutions at genipin concentrations 0-2 mM under moderate change in temperature from 25 to 37°C. The PSC/genipin solutions exhibited fluidity at room temperature for at least 30 min, whereas the ASC/genipin solutions rapidly reached gel points. In specific cases PSC would be preferred over ASC as an injectable gel system. The temperature-responsive gelation of PSC/genipin solutions was due to temperature responses to genipin crosslinking and collagen fibril formation. The elastic modulus of the 0.5% PSC/genipin gel system could be adjusted in a range of 2.5 to 50 kPa by the PSC and genipin concentrations, suggesting that a PSC/genipin solution is a potential injectable gel system for drug and cell carriers, with mechanical properties matching those of living tissues.

Fabrication of high-density collagen fibril matrix gels by renaturation of triple-helix collagen from gelatin.

Collagen-based 3-D hydrogels often lack sufficient mechanical strength for tissue engineering. We developed a method for fabrication of high-density collagen fibril matrix (CFM) gels from concentrated solutions of uncleaved gelatin (UCG). Denatured random-coil UCG exhibited more rapid and efficient renaturation into collagen triple-helix than cleaved gelatin (CG) over a broad range of setting temperatures. The UCG solution formed opaque gels with high-density reconstituted collagen fibrils at 28-32 °C and transparent gels similar to CG at <25 °C. The unique gelation properties of UCG enabled the encapsulation of cultured cells in CFM of high solid volume (>5%) and elasticity (1.28 ± 0.15 kPa at 5% and 4.82 ± 0.38 kPa at 8%) with minimal cell loss. The elastic modulus of these gels was higher than that of conventional CFM containing 0.5% collagen. High-strength CFM may provide more durable hydrogels for tissue engineering and regenerative medicine.