This study develops multifunctional injectable hydrogels as a dressing utilized for chronic wound treatment. Herein, the important properties related to antibacterial ability and bioactive functions of cell proliferation and tissue regeneration are introduced into hydrogel wound dressing. Exploiting the outstanding roles of tropical plant extracts as well as the biocompatibility of natural polymers, the hydrogels are fabricated from these compositions in the presence of glutaraldehyde crosslinker. The natural compounds of extracts might support additional crosslinkings and/or supply other polymer content to reinforce hydrogel networks, that lead to minimize glutaraldehyde concentration to mitigate its toxicity. Moreover, these hydrogels encapsulating bioactive compounds are expected to exhibit many significantly positive biofunctions in wound treatment.

Theoretical results:
In this study, hydrogel system is fabricated by natural polymers including chitosan and/or gelatin through Schiff-base reaction mechanism with glutaraldehyde playing a role of crosslinker. Due to glutaraldehyde residues after hydrogel formation, chitosan and/or gelatin-based hydrogels exhibit effectively antibacterial characteristics. However, high glutaraldehyde concentration is harmful for normal cells and/or other living organs/tissues. The control of glutaraldehyde amount must satisfy both non-toxicity requirements and antibacterial purposes while hydrogel properties should be maintained. The presence of tropical plant extracts is hypothesized to reinforce hydrogel networks and to enhance bioactive function through additional interactions and bioactive functions of natural compounds in plant extracts without an increase of glutaraldehyde concentration.
The optimal formulas of chitosan/Aloe vera extract hydrogels were defined with specific glutaraldehyde content. The remarkable properties of these hydrogel formulas were proven, such as:
- The in situ forming chitosan/Aloe vera-glutaraldehyde hydrogels were able to achive the comparable hydrogel characteristics with chitosan only hydrogels fabricated by 4-fold higher glutaraldehyde concentration. The gelation time was fast and simply controlled by changing the Aloe vera content, the polymer concentration, and the amount of glutaraldehyde.
- Hydrogel system achieves high water retention, good absorption, and good ventilation.
- The chitosan/Aloe vera-glutaraldehyde hydrogels release the natural nitrite amount from 24,0 to 89,6 μM within the first hour for antibacterial activity, then continuously deliver a few μM every next hour for cell activities or cardiovascular treatments.
- The chitosan/Aloe vera-glutaraldehyde hydrogels could kill the planktonic bacteria and prevent bacteria attachment on hydrogel surface effectively (both Staphylococcus aureus and Escherichia coli). Although the chitosan/Aloe vera-glutaraldehyde hydrogels consumed only 0,25% glutaraldehyde concentration, their antibacterial capacities were comparable to chitosan-only hydrogels with 2% glutaraldehyde.
- These hydrogels possess a biodegradable ability.
-The chitosan/Aloe vera-glutaraldehyde hydrogels using 0,25% glutaraldehyde concentration induce the human dermal fibroblasts proliferation significantly. All chitosan/Aloe vera-glutaraldehyde hydrogels with glutaraldehyde crosslinker less than 1% showed non-cytotoxicity.
The optimal formulas of gelatin/Centella asiatica extract hydrogels were found and their remarkable properties were proven, as following:
- Gelatin/Centella asiatica extract hydrogels were in situ formed hy Schiff base reaction. Their gelation time was fast and easily controlled from 1 to more than 30 minutes by varying a composition ratio.
- Hydrogel system achieves high water retention, good absorption, and good ventilation. The gelatin/aqueous Centella asiatica leaf extract-glutaraldehyde hydrogels exhibited microarchitecture and high porosity.
- Gelatin/Centella asiatica extract hydrogels exhibit a good cell compatibility. All hydrogel formulas formed by glutaraldehyde not larger than 0.5% show high cell viability. Especially, the hydrogel composed of 2.5 wt% gelatin, 0.25 wt% extract, and 0.25 wt% glutaraldehyde enhances cell proliferation.
Applied results: Exploiting the abundant sources of tropical plants, the new hydrogel system were developed and exhibited many outstanding functions, that is very potential for biomedical applications in common, for wound dressing in specific. Especially, these hydrogels might be suitable for chronic wounds to prevent the inflammation and accelerate the healing rate.

- Applying herbal plant extracts/broths into hydrogel fabrication is to form products for biomedical applications, specifically for wound care in chronic wound treatment.
- It is the first time in Vietnam, the new hydrogel formulas including chitosan/Aloe vera extract hydrogels or gelatin/Centella asiatica extract hydrogels were successfully fabricated and were carefully characterized.
- The chitosan/Aloe vera extract hydrogels are able to slowly release nitrite which is a NO donor. The generation of NO in living body is very meaningful for treatment of deseases related to cardiovascular systems, inflammation, or immunogenic reaction.
- These hydrogel systems can release polyphenols or other naturally bioactive compounds, which exhibit many outstanding fuctions such as antiaging ability, free radical scavenging to prevent/treat some deseases related to over generation of free radicals.

- Scientific papers in referred journals (list):
+ The international publication in ISI journal: Self-antibacterial chitosan/Aloe barbadensis Miller hydrogels releasing nitrite for biomedical applications, Thai Thanh Hoang Thi et al., Journal of Industrial and Engineering Chemistry, Volume 103, 25 November 2021, Pages 175-186
+ The national publication being written by english: Preparation and characterization of gelatin-based hydrogels encapsulating Centella asiatica extract for biomedical applications, Thai Thanh Hoang Thi et al., Vietnam Journal of Science and Technology.
- Technological products (describe in details: technical characteristics, place): 01 patch of chitosan/Aloe barbadensis Miller hydrogel
- Other products (if applicable): supervise 1 master of chemical engineering.