Ask： What is the difference between EFL-HAMA-150K and EFL-HAMA-400K?

Answer： ① The molecular weight of HAMA-150K is 150KDa, and the molecular weight of HAMA-400K is 400KDa. ② Under the same conditions, the solution viscosity of HAMA-400K is much higher than that of HAMA-150K. The strength of the hydrogel after curing at HAMA-150K is stronger than at 400K, but it is more brittle than at 400K. In other words, HAMA-400K hydrogels are tougher.

Ask： How is HAMA saved?

Answer：Dry skit: room temperature, 3 months; 4℃, 12 months; -20℃, 18 months. Sterile solution: 4°C (in dark), 7 days; -20℃ (in dark), 6 months.

Ask：Why does 5% (w/v) HAMA-150K dissolve in less than 1h, but 2% (w/v) HAMA-400K not?

Answer：The dissolution rate is related to the molecular weight, the molecular weight of HAMA-400K is relatively larger and the dissolution rate is relatively slower. Magnetic agitation is needed to promote dissolution. The solution of 2% (w/v) HAMA-400K is very viscous, and the viscosity of the liquid after complete dissolution is much higher than that of the 5% (w/v) HAMA-150K solution. Normally, HAMA-400K can be completely dissolved in 1-2h by magnetic stirring. If you can't dissolve 2% (w/v) HAMA-400K for half a day, there may be the following reasons: ①There were errors in the way the dissolution was carried out. On the one hand, too little liquid may have been prepared and failed to submerge the rotor. On the other hand, the material was not broken down into smaller pieces and put into dissolution in batches. This is because when the material is too large, a sticky gel layer forms on the surface of the material, which prevents the liquid from soaking in and slowing down the dissolution rate. ②The dissolution process is not protected from light. During the dissolution process, it is necessary to coat the outside of the container with aluminum foil. The gel point of HAMA is very short, and the weak light of 365-405nm can cause partial cross-linking. During the dissolution process, sunlight exposure or long-term exposure to light should be avoided to avoid gelation of dissolved surface materials during the dissolution process, which may affect the further dissolution of the material.

Ask：What sterilization methods are available for HAMA hydrogel solutions?

Answer： ①HAMA is a polysaccharide with relatively stable performance. Commonly it can be filtered and de-bacterized by using a 0.22um filter membrane. ② If the HAMA concentration is high, or you do not want filter sterilization, pasteurization can be used. Additionally, sterilization can also be carried out by autoclaving at 121°C for 20 min. However, it is best not to sterilize the whole process for more than 3h to avoid persistent high temperatures which can cause significant molecular chain breaks and affect the curing effect. ③ Materials cannot be sterilized directly under ultraviolet irradiation, as this may cause cross-linking of the material and lead to poor dissolution properties. PS: Cured hydrogel scaffolds can be irradiated and sterilized with no significant effect on performance.

Ask：What are the functional groups on the HAMA molecule? I'd like to make further modifications, such as grafting drugs, etc.

Answer：HAMA molecules contain a large number of carboxyl and hydroxyl functional groups, among which carboxyl is most commonly used for functionalization modification and can be coupled to specific molecules through esterification or amidation reactions.

Ask： I use HAMA to prepare microneedles and want to distinguish the tip from the substrate. How should I take photos?

Answer： If you are using a camera or a microscope to take a physical picture, you can use different colors of dye to stain the hydrogel, so that the structure of the hydrogel is more recognizable. EFL has developed anti-diffusion hydrogel dyes (Catalog No.: EFL-DYE -ND), with five colors for choice, red, green, blue, yellow, and purple. The dye has a good anti-diffusion ability. These dyes have good anti-diffusion properties and visualize the different hydrogel forms. You only need to stain the tip of the needle and the substrate material separately. If you want to take fluorescence pictures, you can use alkene coupling fluorescent dyes (Catalog No.: EFL-DYE-UF-ENE series) to stably label the HAMA with different colors of fluorescence, and prepare the tip substrates separately.

Ask： Which type of HAMA should be chosen when doing applications with different directions?

Answer：Generally, EFL-HAMA-150K is used for the projection light solid printing or two-photon finishing forming, with a concentration of 5%-10% (w/v). Both types of HAMA can be used for extrusion printing, but when printing usually needs to compound other materials. Specific selection can be determined according to requirements. It is better to choose EFL-HAMA-400K for 3D cell culture, the use of concentration in 0.5~2% (w/v), among which 0.5% to 1% (w/v) is recommended. EFL-HAMA-150K can be used to make spray-thin layers. EFL-HAMA-400K is preferred for wound dressing, pre-crosslinking injectable hydrogel, and coating. For the preparation of hydrogel micro-needles EFL-HAMA-150K is preferred, which is easier to operate, and 5% (w/v) concentration is commonly used (microneedle preparation tutorial). And for other applications, please refer to the physical and chemical properties of the product and select the appropriate type and concentration for testing as required.

Ask：Can cells adhere to the surface of HAMA after light curing? Is there a solution?

Answer：There are no cell adhesion sites on the HAMA surface, so cells cannot adhere directly to the HAMA hydrogel surface. You can modify HAMA according to your experimental needs, for example by grafting RGD peptides onto HAMA molecules. Alternatively, you can purchase EFL's acryloylated RGD peptide (Catalog No.: EFL-PEP-RGDfKAC). The RGD peptide can be grafted directly onto HAMA stably by photo-crosslinking, which can improve the cell adhesion properties of the material.

Ask：What is the adhesion performance of HAMA on tissue surfaces? Can HAMA be used as a glue instead of a surgical suture?

Answer：HAMA solution with high molecular weight is very viscous and has good adhesion performance on the surface of damaged tissues, which is suitable for wound dressing. The adhesive properties and strength of HAMA after curing cannot meet the requirements of replacing surgical sutures. However, there are abundant modifiable groups on HAMA, which can be further modified to make the chemical modification. Alternatively, the adhesion of HAMA can be improved by constructing a composite hydrogel, offering the possibility of using it as an adhesive.

Ask： Is it possible to culture cell micromasses with HAMA without cell adhesion sites?

Answer：Yes. Specific formwork can be printed by using projection light-curing printers (Catalog No.: EFL-BP-86 series) and HAMA hydrogels. These modules have a fixed-size spherical groove structure. When the target cells are inoculated on the form, the cells could spontaneously fall into the spherical grooves and converge into clusters for growth, so that regular cell clusters could be cultivated.