Study On Hydrogel Tissue Expander For Expanded Soft Tissue In The Craniofacial Region

Objective: The aim of this research is to develop a kind of self-swelling soft tissue expander,that can be used for soft tissue expansion to get extra soft tissue in the craniofacial region.Methods: The self-swelling soft tissue expander was synthesized by mass polymerization of N-Vinyl-2-pyrrolidone (NVP) and Methyl methacrylate (MMA).2,2-Azobisisobutyronitrile (AIBN) was the initiator,Allyl methacrylate (AMA) and Ethylene glycol dimethacylate (EGDM) were the crosslinking agents.The physical and chemical properties and biological properties of the self-swelling soft tissue expander was systematically studied by conventional methods.Optical microscope and scanning electron microscope (SEM) was used to observe the morphology of the hydrogel.The swelling rate of the hydrogel was determined by weighing method.The compressive strength of the hydrogel was tested by universal mechanical testing machine.The chemical structure of the hydrogel was tested by the infrared spectroscopy and the element composition was analyzed by an energy spectrum analyzer.The biosafety of the hydrogel was evaluated in the maxillofacial region of SD rats,and the basic situation of hydrogel in vivo imaging was evaluated by color doppler ultrasound,spiral CT and Magnetic Resonance Imaging (MRI).Results: With N-vinyl pyrrolidone (NVP) and methyl methacrylate (MMA) as monomer,hydrogel formulations and reaction conditions synthesized by bulk polymerization can obtain ideal polymer compounds.The polymer can be used as a soft tissue expander.The expander is shell-free,reshapable,highly resilient,good compressive properties and biological safety.The morphology observation indicates that the hydrogel is uniform and transparent,with no obvious defects in structure,uniform distribution of micropores,and a three-dimensional network structure after expansion.The initial expansion of the hydrogel requires 3-4d and 7d to expand completely,and the swelling rate is 505.87%±3.6%.After full expansion,the compressive strength was 1.79 + 0.20 MPa.The energy spectrum analysis shows that the hydrogel contained C and O elements,and the distribution is uniform.Fourier transform infrared spectroscopy shows that hydrogel contained carboxyl and ester groups.The animal experiments on maxillofacial region of SD rats shows that they have good biocompatibility,expanded soft tissue and gradually formed envelopes around the hydrogel.Radiography shows that the hydrogel have good imaging function in color Doppler ultrasound,spiral CT and magnetic resonance imaging.Conclusions: The formula obtained in this research is feasible and is expected to be the basic formula of the maxillofacial soft tissue expander.The physicochemical and biological safety of the hydrogel synthesized can basically meet the requirements of the maxillofacial soft tissue expansion.However,further research is necessary,such as formulation optimization,performance testing,animal experiments and clinical research.