A review of complications of polyacrylamide hydrogel injection

Once a popular injectable filler,polyacrylamide hydrogel(PAAG)has been banned in China since 2006 due to its unclear safety and long-term complications.However,it is still being used worldwide because of its huge commercial profit,leading to emerging complications and an urgent need for standardized clinical management.This review aimed to assess the properties,safety,and complications of PAAG and treatment strategies for its removal.

Determination of Residual Acrylamide in Medical Polyacrylamide Hydrogel by High Performance Liquid Chromatography tandem Mass Spectroscopy

Objective To determine residual acrylamide in medical polyacrylamide hydrogel by high performance liquid chromatography tandem mass spectroscopy （HPLC-MS）. Methods After 13C3 labeled acrylamide was added, the sample was extracted with water and then cleaned up with ExtrelutTM 20. The polyacrylamide hydrogel sample and 20 clinical cases were analyzed by HPLC-MS/MS and isotope dilution quantifying technique in selected reaction monitoring （SRM） mode. Results Acrylamide was separated from polyacrylamide hydrogel. The concentration of acrylamide in polyacrylamide hydrogel ranged from 3.9×10^-9 to 3.1×10^- 8g/L in the 20 clinical cases. The peak area was favorable linear and the range was up to 3 000 μg/L. The recovery rate was 103.1% with a relative standard deviation （RSD） of 6.20%, when the mark level was 50 lag/L. Conelusion HPLC-MS is a rapid, accurate, and sensitive method for the determination of residual acrylamide in medical polyacrylamide hydrogel.

ADDITIVE-INDUCED ENHANCEMENT OF OPTICAL CLARITY OF POLYACRYLAMIDE HYDROGEL

The aqueous polymerization of acrylamide and crosslinking with N,N-methylenebisacrylamide afforded hydrogelsdisplaying high levels of light scattering (poor optical clarity). Enhancement of the optical clarity within a polyacrylamide(PAm) hydrogel was accomplished through the implementation of 'refractive index matching'. Water-soluble additives wereutilised to better match the refractive index inhomogeneities throughout a given hydrogel. This resulted in lower lightscattering within the system and hence improved clarity. Amino acids, sugars, polymers, and other water-soluble additivessuch as glycerol were investigated by this methodology. Most additives investigaed displayed potential for effectivelyreducing the light scattering within a PAm hydrogel as a function of increased additive concentration. On increasing therefractive index of the water medium, the overall refractive index of a PAm hydrogel was also observed to increase. Thisprovided a quantitative means of determining the effectiveness of a given additive for improving the optical clarity within ahydrogel.

Polyacrylamide gel migration after injection for breast augmentation:A case report

Polyacrylamide hydrogel(PAAG)was once considered a safe,reliable,and compatible injected filler and was widely used in breast augmentation,rhinoplasty,and other cosmetic surgeries.However,numerous complications,such as implant migration,have been observed after PAAG injections.Herein,we report a rare case of distant implant migration after PAAG injection for breast augmentation in which the material became displaced along the abdominal wall to the perineum and pelvic extraperitoneal space.After a well-prepared preoperative evaluation involving magnetic resonance imaging(MRI)and computed tomography(CT)examinations and threedimensional hologram,debridement surgery was performed to remove the injected material.After the operation,the patient was followed up for two years and was not scheduled for a second operation.Postoperative complications of breast augmentation after PAAG injection,especially gel migration,still affect thousands of patients.Once material migration occurs,surgical removal becomes difficult.Early diagnosis and treatment are recommended.

Hydrogel-based optically and mechanically manipulable broadband microwave absorber

Microwave absorbers with unique optical and mechanical performance are urgent for complex electromagnetic environment.Here,we demonstrate the mechanically flexible,optically transparent,and microwave-absorbing polyacrylamide(PAM)hydrogel,in which the polar water molecules with high polarization contribute to the efficient microwave attenuation,but the binding between water molecules and PAM will slow down the orientation polarization of polar molecules.Meanwhile,the dominated dielectric property of water molecules in PAM hydrogel determines that the molecules displacement in polymer mixture is feasible for manipulating permittivity.Besides,by decreasing temperature,the flexible and transparent hydrogel will switch to rigid and opaque state as the phase conversion between amorphous and polycrystal state.By constructing structures with such hydrogel,the obtained absorber also exhibits the optical and mechanical switchable properties,covering the effective absorption within 5.7-18 GHz.This work provides an effective method to fabricate optically and mechanically manipulable microwave absorbers for intelligent electromagnetic stealth systems.

Response of Photonic Hydrogels of Homogeneous Particles to Uranyl Ions in Aqueous Solutions

We study here the response of photonic hydrogels(PHs),made of photonic crystals of homogeneous silica particles in polyacrylamide hydrogels(SPHs),to the uranyl ions 22 UO_(2)^(2+) in aqueous solutions.It is found that the reflection spectra of the SPH show a peak due to the Bragg diffraction,which exhibits a blue shift in the presence of 22 UO_(2)^(2+).Upon exposure to the SPH,22 UO_(2)^(2+)gets adsorbed on the SPH and forms complex coordinate bonds with multiple ligands on the SPH,which causes shrinking of hydrogel and leads to the blue shift in the diffraction peak.The amount of the blue shift in the diffraction peak increases monotonically up to 22 UO_(2)^(2+)concentrations as high as 2300μM.The equilibration time for the shift in the Bragg peak upon exposure to 22 UO_(2)^(2+)is found to be~30 min.These results are in contrast to the earlier reports on photonic hydrogels of inhomogeneous microgel particles hydrogel(MPH),which shows the threshold 22 UO_(2)^(2+)concentration of~600μM,below which the diffraction peak exhibits a blue shift and a change to a red shift above it.The equilibration time for MPH is~300 min.The observed monotonic blue shift and the faster time response of the SPH to 22 UO_(2)^(2+)as compared to the MPH are explained in terms of homogeneous nature of silica particles in the SPH,against the porous and polymeric nature of microgels in the MPH.We also study the extraction of 22 UO_(2)^(2+)from aqueous solutions using the SPH.The extraction capacity estimated by the arsenazo-III analysis is found to be 112 mM/kg.

Transparent h-BN/polyacrylamide nanocomposite hydrogels with enhanced mechanical properties

In this study, a facile way has been proposed to prepare transparent, tough and flexible polyacrylamide （PAM） hydrogels which is composed of a dually crosslinked single network by chemical crosslinking of N,N＇-methylenebisacrylamide （BIS） and physical crosslinking of hydrophilic hexagonal boron nitride （h- BN） nanosheets. The resulting h-BN/PAM nanocomposite hydrogels are highly transparent, and exhibit significantly enhanced mechanical properties compared to the dark （GO）/PAM nanocomposite hydrogels or chemical crosslinking PAM hydrogels. Thus it opens up new opportunities for developing next- generation transparent, tough and flexible hydrogels that hold great promise in such important applications as light responsive soft robot and liquid microlenses.