alginate Archives - Perfect 3D Printing Filament

Continuous Chaotic 3D Printing: Using Chaos Theory to Control Microstructures

Researchers continue to experiment with materials and extrusion techniques, introducing the use of chaotic flows for improved microarchitectures in the recent study, ‘‘Using chaotic advection for facile high-throughput fabrication of ordered multilayer micro- and nanostructures: continuous chaotic printing.’

The authors present a unique form of fabrication with a method that allows for more precise control of the structure and surface area being printed through the use of what they call ‘continuous chaotic printing.’ The process relies on a combination of chaos theory and fluid dynamics, in which the flow of material develops into complex fractals. To achieve this, the team created chaotic material flows by reorienting and splitting fluid as it is mixed, as shown in the figure below.

With a focus on multiple materials, multiple layers, and fabrication of varying cells in proximity to each other on larger surfaces, their goal was to test the potential for chaotic printing in a variety of applications, but with a special focus on bioprinting and biomedical research. Building on previous research with chaotic flow, the authors experimented with a chaotic printer (paired with a Kenics static mixer), fabricating fibers made from alginate.

Experimental setup. Continuous chaotic printing is based on the ability of a static mixer to create structure within a fluid. The Kenics static mixer (KSM) induces a chaotic flow by a repeated process of reorientation and splitting of fluid as it passes through the mixing elements. (A) Schematic representation of a KSM with two inlets on the lid. The inks are fed at a constant rate through the inlets using syringe pumps. The inks flow across the static mixer to produce a lamellar structure at the outlet. The inks are crosslinked at the exit of the KSM to stabilize the structure. Our KSM design includes a cap with 2 inlet ports, a straight non-mixing section that keeps the ink injections independent, a mixing section containing one or more mixing elements, and a nozzle tip. The lid can be adapted to inject several inks simultaneously. (B) Two rotated views at 0◦ and 90◦, of a single KSM element. (C) 3D design of a KSM with 6 elements and schematic representation of the flow splitting action, the increase in the number of striations, and the reduction in length scales, in a KSM-printhead. The resolution, namely the number of lamellae and the distance between them (δ), can be tuned using different numbers of KSM elements. (D) Actual continuous chaotic printing in operation. The inset (E) shows the inner lamellar structure formed at the cross-section of the printed fiber (the use of 4 KSM elements originates 16 striations). Scale bar: 250 µm. (F) Longitudinal or (G) cross-sectional microstructure of fiber obtained using different tip nozzle geometries. Images show CFD results of particle tracking experiments where two different inks containing red or green particles are coextruded through a printhead containing 4 KSM elements. The lamellar structure is preserved when the outlet diameter is reduced, from 4 mm (inner diameter of the pipe section) to 2 mm (inner diameter of the tip), through tips differing in their reduction slope.

An unlimited number of inks can be used in chaotic printing, but for this study, the researchers used basic techniques, with sodium alginate as a base. Experiments were then performed with composite inks featuring suspensions like polymer microparticles, graphite microparticles, mammalian cells, or bacteria. Ultimately, the team reported they were able to print ‘fine and well-aligned microstructures’ at high extrusion speeds of 1–5 m of fiber/min.

“This printing strategy is also robust across a wide range of operation settings. We conducted a series of printing experiments at different inlet flow rates to assess the stability of the printing process. As long as the flow regime is laminar and the fluid behaves in a Newtonian manner, the quality of the printing process is not affected by the flow rate used in a wide range of flow conditions,” explained the authors.

Evaluation of the striation profiles and mechanical properties of chaotically printed alginate/graphite fibers. (A) Lamellar microstructure of fibers produced with printheads containing 2, 3, 4, 5, or 6 KSM elements. The thickness of each lamella, along the red line, was determined by image analysis using Image J (shown below each cross-sectional cut). Scale bar (red): 2 mm. (B) The microstructure at each cross-section was reproduced by CFD simulations, and the thickness and position of each lamella was calculated. (C) Striation Thickness Distribution (STD) and (D) cumulative STD for constructs printed using 4, 5, 6, and 7 KSM elements. (E) Comparison of stress-strain curves of fibers fabricated by extrusion of pristine alginate and graphite without chaotic mixing (marked as hand-mixed) or with chaotic printing using 2, 4, or 6 KSM elements (marked as 2, 4, or 6 ke). (F) Comparison of the standard deviation of tensile properties (i.e. maximum stress, maximum strain, and Young’s modulus for the same set of fibers; 5 fibers per treatment).

The researchers also noted the following while printing:

Stable fibers were printed using a cone-shaped nozzle tip with an outlet diameter of 1 mm, with flow rates ranging from 0.003 to 5.0 ml min−1.
Printheads with varying geometries did not affect structures being printed.
Computational fluid dynamics (CFD) showed that the inclination of the nozzle tip also did not affect the materials.

Continuing to emphasize the ‘robust’ qualities of chaotic printing—especially when used with small nozzles—the researchers were able to control resolution, noting also that, due to the deterministic qualities of chaotic flows, fabrication of structures was ‘fully predictable.’ Resolution was in part illustrated by the number of gill-like ridges, or ‘lamellae,’ created through the chaotic mixing process.

“As the number of elements used to print increased, the number of lamellae observed in any given cross-sectional plane of the fiber also increased, while the thickness of each lamella decreased,” explained the researchers. “Therefore, users of continuous chaotic printing will have more degrees of freedom to determine the multi-scale resolution of a construct, as this is no longer mainly restricted by the diameter of the nozzle (or the smallest length-scale of the nozzle at cross-section).”

Bioprinting of living micro-tissues: (A) Optical and (B) SEM micrographs of the cross-sectional view of a construct in which C2C12 cells are chaotically bioprinted in an alginate/GelMA hydrogel using a 3-KSM printhead; Scale bars: 500 µm and 50 µm, respectively. (C) Longitudinal view of a chaotically bioprinted construct; a high cell viability is observed at the initial time, as revealed by a live/dead staining and fluorescence microscopy. Scale bar: 500 µm. Inset shows a cross-sectional cut. Scale bar: 500 µm. (D) Cells spread along the chaotically printed striations, preserving their original positions after 13 d of culture. Scale bar: 200 µm. (E) Optical microscopy view of a segment of fiber containing C2C12 cells 18 d after printing. Scale bar: 500 µm. (F) Close-up of a region stained to reveal F-actin/nuclei, showing the cell spreading and the formation of interacting cell clusters. Cell nuclei can be identified as blue dots. Actin filaments appear in red. Scale bar: 200 µm.

Further, as the researchers began experimenting with bioprinting, they were able to create alginate fibers rich with cells, and lightly enriched with protein to encourage ongoing sustainability. This is one of the greatest challenges in tissue engineering. Even though the correct materials, techniques, and concepts may be in place, if researchers cannot keep the cells alive long enough, they must go back to the drawing board.

Altogether, the team suggests that it has developed a completely novel way to control the resolution of an extrusion-based printing system. As shown in the image below, not only can this continuous chaotic printing process control print resolution through the diameter of the nozzle, but at the microscale as well through the chaotic mixing techniques deployed.

Development of multi-scale architectures based on 3D continuous chaotic printing: (A)–(C) 3D printing of hydrogel constructs using a KSM-printhead integrated to a commercial cartesian 3D printer. (A) Schematic comparison of the lack (prepared using conventional extrusion techniques) and presence of internal lamellar microstructures (developed using continuous chaotic printing). (B) Printing of a long fiber arranged into a macro-scale hydrogel construct (3 cm × 3 cm × 4 mm). Scale bar: 5 mm. (C) Transverse cut of the macro-construct showing the internal microstructures. Scale bar: 1 mm. (D)–(G) Chaotic printing of fibers coupled with electrospinning. (D) Schematic representation of the coupling between continuous chaotic printing and an electrospinning platform; an ink composed of a pristine alginate ink (4% sodium alginate in water) and an ink composed of a polyethylene oxide blend (7% polyethylene oxide in water), were coextruded through a chaotic printhead and electrospun into a nanomesh. (E) AFM image showing the diameter of three individual nanofibers ((1) 0.82 µm, (2) 1.05 µm, and (3) 0.437 µm) within the electrospun mesh. Scale bar: 5 µm. (F), (G) photo-induced force microscopy (PiFM) reveals the lamellar nature of the nanostructure within a nanofiber (white arrows) originated using (F) a 2-element KSM printhead, and (G) a 3-element KSM printhead. Scale bar: 1 µm.

The researchers noted that not only could this have a profound impact on multimaterial printing technologies, but on bioprinting as well:

“Our results demonstrate the unrivaled ability of chaotic printing to deploy cells within high SAV fibers. As available bioprinting and bioassembly technologies approach the resolution and SAV of chaotic printing, they also tend to require long fabrication times and mechatronically coordinated control systems,” concluded the researchers. “In addition to multicellular, high SAV constructs, chaotic printing offers other breakthroughs in regards to currently available multimaterial printing technologies that, typically, require optimized inks that must be deployed under a specific and narrow range of conditions.”

[Source / Images: ‘Using chaotic advection for facile high-throughput fabrication of ordered multilayer micro- and nanostructures: continuous chaotic printing’]

The post Continuous Chaotic 3D Printing: Using Chaos Theory to Control Microstructures appeared first on 3DPrint.com | The Voice of 3D Printing / Additive Manufacturing.

Omid Afarinan is Bioprinting in Iran

When we were assembling our bioprinting world map, we omitted some companies. We are adding to that map and will continue to do so until we have everyone. One of the firms that we did not initially find is Omid Afarinan, also known as 3D Bio. This is an Iranian firm that makes bioprinters and bioinks. We have thus far seen comparatively little 3D printing and bioprinting activity in Iran, so we were more than happy to do an interview with the firm to find out more (as well as apologies for forgetting them in the world map!).

What does your company do?

Our company works on the whole bioprinting chain from tissue design to application stage. The focal point of our efforts in this chain is design, fabrication and development of commercial bioprinters. All research and development attempts are defined based on the targeted tissue or in other words the tissue need and market trend. Based on this fact, the target tissue determines the customization of the bioprinters, the choice of living cells and bioinks creating a multi-disciplinary ecosystem of scientific fields.

Where do you hope to be in five years?

Our mid-term goal in the next five years is turning into a leading company in bioprinting research and development with several specialized laboratories and the sole bioprinting service hub. Achieving the first transplantable living tissue would be the ultimate goal in this period.

Why should someone choose to work with you?

Our team has the capability of creating a wide range of customizations in bioprinter design both on the hardware systems and software. This capability leads to customer-made versions and tissue-specific printers. Our bioprinters are of high quality and competitive to its foreign counterparts from the accuracy and cost point of view. Our exemplary teamwork among various experts and the existence of a multi-profession environment led to current achievements and also resulted in training talented trainees. Our team welcomes specialized groups and eager students especially in the field of molecular and cellular biology to strengthen its abilities.

What are the differences between the Biofab and the Pioneer series?

The main difference between these series is their printing mechanism. The Pioneer bioprinter is extrusion-based using screws while Biofab utilizes pneumatic actuators for printing. This, in turn, makes Biofab more capable especially in the case of accuracy. The Pioneer version possesses the ability of unparalleled control over print heads and can print a variety of hydrogels. Moreover, the Biofab version supports a wide range of biomaterials and viscous cell suspensions for printing.

Both series provided in two versions, with 2 or 4 printing heads.

What kind of bioinks have you developed?

Omid Afarinan, as the first national company in Iran, has gathered experts from different fields of science with the aim of producing novel bioinks. Omid Afarinan bioinks are cost-effective, have high printability, mimic extracellular matrix (ECM) and provide a suitable environment for cell proliferation, growth, and differentiation. Some of the new unique bioinks of the 3D-Bio Team are PCL, PCL/Starch, Alginate and Alginate/Gelatin bioinks. Soft-Ink is the newest bioink of the company; a biodegradable bioink based on pure Alginate and Gelatin which can support growth and proliferation of any cell type of soft tissues. One of the main features of this bioink is high printability and uniformity with the ability to adjust the stiffness of its printed matrix.

In addition to a variety of bioinks from thermoplastic materials to hydrogels, the company also produces custom-made bioinks for specific applications.

What are customers doing with your printers?

The customers mainly use the printer for conducting state-of-the-art researches especially on creating regenerative tissues for transplantation and studying the behavior of living tissues. In particular, our current customers work on hard tissue as bone scaffold especially maxillofacial and soft tissue including cartilage, skin, cornea and heart. The study on drug delivery, cosmetic research and cancer treatment are other aspects of what our customers do with bioprinters.

What short term successes do you see occurring in bioprinting?

Successes in bone and cartilage tissues are promising in recent years. This is due to the fact that such tissues have low cell densities. This is more pronounced in the bone tissue where acellular scaffolds can be used. Skin printing comes next in the list on the soft tissue side, for being a flat and multi-layered tissue. Also, Bioinks are being developed in parallel but at a slower pace. These short-term successes would pave the path for tissues with more complex geometries.

Where is bioprinting challenging?

The challenges exist in both pre- and post-printing stages of bioprinting. At pre-printing stage, the challenge is on the printability of biomaterials and Bioinks. In other words, making the materials printable and the suitability of the printing is of prime importance. Overcoming this challenge leads to printed functional tissues that could mimic real ones. On the post-printing stage, the challenges mainly arise from the complexity in living tissues especially vascularization and post-printing processes such as cell culture and migration that makes the printed tissues ready for their applications. These challenges and issues need close collaborations between different experts to resolve in short and long-term periods.

What advice would you have for a researcher wanting to get into bioprinting?

The first advice is that the researcher should wear iron shoes. In other words, facing many difficulties is unavoidable and gaining achievements may take time. So, patience and being hopeful is the key point. Furthermore, bioprinting requires a multi-disciplinary group including engineers, biologist and doctors and no one can individually succeed in this path. Finally, utilizing a standard and reliable bioprinter could be beneficial and time-saving for any researcher.

The post Omid Afarinan is Bioprinting in Iran appeared first on 3DPrint.com | The Voice of 3D Printing / Additive Manufacturing.

REGEMAT 3D Will Start Selling Biomaterials

One of the key players in the bioprinting field in Spain will be incorporating seven new biomaterials. In the coming months, REGEMAT 3D will launch a catalog of biomaterials that customers can buy and use along with their bioprinting systems. According to company officials, in recent years, advances in 3D bioprinting systems have become very important, as well as new biomaterials for regenerative medicine. The performance of the research groups with which they collaborate has produced results that were likely unheard of years ago. Still, they consider that these innovations in bioprinting systems must be accompanied by a progressive definition and characterization of the biomaterials being used. This year, one of REGEMAT 3D’s objective is to advance biomaterials for further research in the different applications derived from the 3D bioprinting sector, which is growing every year.

REGEMAT 3D bioprinting with new biomaterials

Each specific application requires different solutions and appropriate biomaterials to optimize processes. For instance, it is easy to understand that to regenerate skin components, hydrogels, cells and growth factors are different from those needed to regenerate muscle tissue, bone or cornea. So, it is essential to offer researchers and scientists different biomaterials to aid their work. REGEMAT is focusing on seven: thermoplastics, collagens, alginates, agaroses, gelatin methacryloyl (GelMA), nanocellulose, and different types of cell media compatible with the cells used. All of the biomaterials should be easy to print, handle and will allow researchers to tackle some of the challenges they face while working.

The new biomaterials for 3D bioprinting will be available on the company’s web page (which they will relaunch shortly), as well as through their offices. REGEMAT 3D has agreements with several national and international partners for the manufacture of these products. The first ones to be sold commercially will be nanocellulose, collagen, and alginate.

REGEMAT 3D new biomaterials

The Granada, Spain-based biotech company has sold its machines to users in more than 25 countries. For years, the company has been working with research groups at the University of Granada in advanced therapies, participated in a joint project for the development of new therapies for cartilage regeneration, and has collaborated with the University Hospital of La Paz, where REGEMAT 3D’s founder coordinates the 3D Tissue Engineering and Printing Platform (PITI3D), which provides ingredients and processes to generate functional tissues. Since its origin, the startup has been focusing on regenerative medicine, developing custom hardware and software required and demanded by some of the major hospitals and research universities in the region. They develop their own bioprinting systems – the BIO V1 machines – and customize them for their users’ applications according to the requirements of each investigation.

Last January, a group of researchers led by the University of Granada and REGEMAT 3D, published an academic article on the development of a volume-by-volume 3D biofabrication process that divides the printed part into different volumes and injects the cells after each volume has been printed, once the temperature of the printed thermoplastic fibers has decreased. This helps overcome problems that arise when working in 3D bioprinting with thermoplastics at high temperatures: one of the biomaterials they will soon begin commercializing, with which the company is very familiar and has worked with for a long time.

To continue developing new biomaterials and launching new products, the Spanish company, led by founder and CEO José Manuel Baena, has managed to raise 320,000 Euros in the midst of the latest financing round. REGEMAT 3D, along with its sister company Breca, are not only launching the new series of biomaterials, but they are also expanding their presence to Brazil, where the company has already started to market its products, and China, where they closed an agreement with Chinese distributor ApgBio, based in Shanghai, that’s responsible for introducing bioprinting equipment in the country for the regeneration of organs or tissues. Companies like REGEMAT 3D are gearing up to mass produce biomaterials, providing researchers with more options when it comes to bioprinting for regenerative medicine and advanced therapies, usually keeping in mind how patients bodies will react to the new materials, and whether they will be compatible. Spain, like many other European countries, is quickly catching up to the world of bioprinting, which today is led by US-based companies but shows promise in many developed countries.

[Images: REGEMAT 3D]

The post REGEMAT 3D Will Start Selling Biomaterials appeared first on 3DPrint.com | The Voice of 3D Printing / Additive Manufacturing.

Bioprinting 101: Part 4 – Alginate

Alginate is derived from brown algae

Alginate is a polysaccharide distributed widely in cell walls of brown algae. When it bonds with water it typically forms a viscous gum. Alginate absorbs water quickly, which makes it useful as an additive. Alginate can be used as a hydrogel as well. It has very interesting applications. It is a hydrogel consisting of microparticles or in bulk gels combined with nerve growth factor in bioengineering research. It has been used as scaffolding for tissue engineering, as a delivery vehicle for drugs, and as model extracellular matrices for basic biological studies. These applications require tight control of a number of material properties including mechanical stiffness, swelling, degradation, cell attachment, and binding or release of bioactive molecules.

The chemical structure of alginate is composed of two types of uronic acid: Mannuronic acid unit (M) and Guluronic acid unit (G). Differences in M/G ratio and block configuration account for the differences in alginate properties and functionality, especially in gelling capability and gel strength. The M/G ratio is dependent upon such factors as is the species of seaweed (imagine the difference of a species found near water around remote East Asian Islands vs. seaweed found in a nice tropical location near the Bahamas), the part of the seaweed used, the harvest location, and the harvesting season. The carboxyl groups within the M and G units are easily ion-exchanged, and can react with several kinds of cations. Cations are essential to consider when it comes to material strength.

Alginate Bioink

Alginates have been used as scaffolds for tissue engineering extensively. We have discussed hydrogels previously within this series, but what makes an alginate different? Alginate based products possess excellent shear-thinning properties, and can be easily extruded through a nozzle. There they also have good initial shape fidelity. Alginate is widely used for most bioprinting extrusion processes due in part to this. There is also a focus on alginate due to the ability to mix materials readily with these extrusion methods. Alginate is biodegradable, has controllable porosity, and may be linked to other biologically active molecules. Encapsulation of certain cell types into alginate beads may actually enhance cell survival and growth. Outside of biodegradability, alginates are also non-toxic. This is vital for biomedical purposes.

Sodium Alginate Chemical Structure

Alginate is a great biomaterial. As with the other biomaterials we have analyzed, it is typically used in combination with other materials. This is related to what we previously mentioned in this article in terms of bioreactivity. It allows a material scientist or engineer to experiment and make substances with various tensile strengths and viscosity levels. With the benefits of alginate, there come some major cons. The most important thing to consider is how much water a hydrogel derived from alginate can contain. Depending on the hydrophilicity, a hydrogel from alginate may not be able to maintain absorbance levels for larger scale builds. This is why we cannot make a bioink or hydrogel from solely alginate. Stay tuned for info on more materials used within bioprinting. This field has such variety within it, so we will do our best to shed a light on important materials and processes.

This article is part of a series that ultimately wants to update 3DPrint.com readers in the most vital and relevant information in bioprinting. We hope that this will prompt people to bioprint at home which in turn may accelerate the bioprinting revolution. Essentially, this article has as its goal to kickstart a DIY bioprinting revolution. Please spread the word. The first article Bioprinting 101 is here, while Part Two Hydrogels is here and part three Industrial printers is here.

Bio-printing 101: How to Bioprint at Home

<em>Picture 2: </em>Hydrogel fabricated by PSL 3D printing technique” width=”565″ height=”314″></p>
<p style= Bioprinted Hydrogels

Bioprinting is an exciting area to follow as it invigorates the ideas of Frankenstein and a bunch of other sci-fi scenarios that make us slightly paranoid. So how does someone create their own monster within their garage? Well, that is pretty far fetched at the moment, but there are ways to get involved in this field in small ways.

Consistently, within bioprinting, there does not seem to be a significant presence within the general maker community. The healthcare industry as a whole is typically private sector driven. So how does someone get the chance to work on 3D bioprinting when they do not even know the resources they need, or how to start?

An essential consideration for 3D bioprinting is the material used for prototyping. Typically 3D printers use different materials to create products such as PLA, ABS, Wood Fiber, PET, PVA, Nylon, and TPU. The issue of creating bioprinted materials is not within the actual structure of the model and design. The problem lies in creating objects that also follow the rules of biology. This limitation forces a material to have specific heating and cooling properties in relation to where it is within the body. Specific heat and tolerance to different temperature ranges are vital in a material used for bioprinting. Even with the creation of 3D structures, there is still a difficulty in replicating the intricate vascular structures of different organs within our bodies. This makes for a variety of problems that need to be worked on within the field of 3D bioprinting in general.

So what are some first steps within 3D bioprinting? Let us focus on some materials that would be ideal to focus on as they are good candidates for current and future use. Here is a list of some current materials used in bioprinting:

Bioink
Hydrogels
Alginate
PEG (polyethylene glycol)
PCL (Polycaprolactone)
PGA (Polyglycolic Acid)
Pluronics

In later articles, we will discuss each material above in more depth. For now we will address them briefly.

Bioinks are substances made of living cells that can be used for 3D printing of complex tissue models. Bioinks are materials that mimic an extracellular matrix environment to support the adhesion, proliferation, and differentiation of living cells.

A hydrogel is a network of polymer chains that are hydrophilic, sometimes found as a colloidal gel in which water is the dispersion medium. A three-dimensional solid results from the hydrophilic polymer chains being held together by cross-links. Alginate is a polysaccharide distributed widely in the cell walls of brown algae, where through binding with water it forms a viscous gum.

Alginate is made from brown seaweed.

Alginate is a polysaccharide distributed widely in the cell walls of brown algae, where through binding with water it forms a viscous gum.

PEG is marketed as a laxative but is also a stabilizing agent in toothpaste.

Polyethylene glycol (PEG) is a polyether compound with many applications, from industrial manufacturing to medicine and is often used in making hydrogels for 3D printing.

Polycaprolactone (PCL) is a bioabsorbable polyester with a low melting point of around 60 °C and a glass transition temperature of about −60 °C.

Polyglycolic acid (PGA) is a biodegradable, thermoplastic polymer and the simplest linear, aliphatic polyester. PGA is used for scaffolds and as a support material.

Pluronics are nonionic triblock copolymers composed of a central hydrophobic chain of polyoxypropylene (poly(propylene oxide)) flanked by two hydrophilic chains of polyoxyethylene (poly(ethylene oxide)).

Now that we understand a little bit about the materials that we can use, it becomes a question of what type of printer to use. Most industrial bioprinters are far from a viable price for consumer purchase. Communities of makers have few options for buying a 3D bioprinter. There also seems to be a lack of internet resources to instruct people on how to bioprint. To help people at home, we will try to build a 3D bioprinting setup with a guide for all those who are interested in bioprinting. As a follow up on this article, be sure to look out for information on the biomaterials mentioned above and separate articles on each of them and how they relate to 3D bioprinting. Stay tuned for more DIY bioprinting tips and tricks.

Marine-Based Hyrdogels Used to Develop New Bioink for 3D Bioprinting

One of the challenges in the field of bioprinting is developing bioinks that are safe and effective. In a paper entitled “Marine Biomaterial-Based Bioinks for Generating 3D Printed Tissue Constructs,” a group of researchers discusses the development of a bioink using alginate and fish gelatin (f-gelatin). They created a marine-based interpenetrating polymer network (IPN) consisting of alginate and f-gelatin methacryloyl (f-GelMA) networks via physical and chemical crosslinking methods, respectively.

“In this study, four different concentrations of alginate (1%, 2%, 3%, and 4%) and three low concentrations of f-GelMA (4%, 5%, and 6%) were investigated and found to form double networked alginate/f-GelMA hydrogels,” the researchers explain. “In the mechanical properties test, the pure alginate hydrogel showed a typical increase in mechanical strength with the increase of concentration and low mechanical strength when its compressive modulus was around 40 kPa, even at 4% alginate, compared with alginate/f-GelMA IPN hydrogel where the modulus of alginate/f-GelMA was approximately 40 kPa at 1% alginate.”

This showed that the mechanical strength of hydrogels was significantly increased by employing an alginate and f-GelMA double network. According to the researchers, the tunable mechanical strength range in alginate/f-GelMA hydrogel would be sufficient to meet the diverse requirements of different tissues.

The researchers also performed swelling tests with pure alginate hydrogel as a control group, and found that the mass swelling ratio decreased with the increase in concentration of alginate.

“For the alginate/f-GelMA hydrogel, the mass swelling ratio for all tested groups was lower than for the pure alginate group,” the researchers continue. “This was due to the increased crosslinking density from the addition of f-GelMA which generated additional polymeric networks via covalent bonding…The swelling properties of hydrogel mainly depend on the hydrogel pore size, polymer concentration, density of cross-linking, and the interaction with solvents.”

The researchers also investigated the degradation characteristics of the hyrdogels. The degradation rate of the alginate/f-GelMA in a saline solution was similar for 2% and 4% alginate, though the 2% degraded faster. The morphology of the hydrogels was tested as well, and the alginate/f-GelMA exhibited a highly porous structure, which can provide enough space for the transport of nutrients and gas exchange for cell survival.

“To assess the cell behavior and examine the feasibility (cell viability, adhesion, and cell proliferation) of alginate/f-GelMA hydrogel, cell adhesion and 3D cell encapsulation assays were performed to examine the ability to bind to alginate/f-GelMA scaffold which is crucial for cell survival,” the researchers state. “…Encapsulated NIH-3T3 cells were cultured for seven days and cell viability was determined using LIVE/DEAD assay kits. As shown in Figure 3C, cells maintained high viability during the culture period (one, three, five, and seven days) and demonstrated that cells can maintain long-term survival rates in alginate/f-GelMA hydrogel.”

The results of the testing showed that alginate/f-GelMA hydrogel has a lot of promise for tissue engineering applications, including 3D bioprinting. To further confirm the morphology and cell viability in the process of 3D printing, a two-layer scaffold was printed and Live/Dead assay was carried out to investigate the cell survival ratio. The scaffold displayed a satisfactory 3D arrangement under microscopy with high cell viability.

This study was the first incidence of using alginate and f-GelMA for 3D bioprinting, and the successful results mean that marine biopolymers could feasibly replace biopolymers from mammalian resources, which can carry diseases or be subject to religious restrictions.

Authors of the paper include Xiaowei Zhang, Gyeong Jin Kim, Min Gyeong Kang, Jung Ki Lee, Jeong Wook Seo, Jeong Tae Do, Kwonho Hong, Jae Min Cha, Su Ryon Chin and Hojae Bae.

Discuss this and other 3D printing topics at 3DPrintBoard.com or share your thoughts below.