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Polyacrylamide (PAAm) hydrogels are widely adopted as 2D‐model soft substrates for investigating cell‐material interactions in a controlled in vitro environment. They offer facile synthesis, tunable physico‐chemical properties, diverse biofunctionalization routes, optical transparency, mouldability in a range of geometries and shapes, and compatibility with living cells. PAAm hydrogels can be engineered to reconstruct physiologically relevant biointerfaces, like cell‐matrix or cell–cell interfaces, featuring biochemical, mechanical, and topographical cues present in the extracellular environment. This Review provides a materials science perspective on PAAm material properties, fabrication, and modification strategies relevant to cell studies, highlighting their versatility and potential to address a wide range of biological questions. Current routes are presented to integrate cell‐instructive features, such as 2D patterns, 2.5D surface topographies, or mechanical stiffness gradients. Finally, the recent advances are emphasized toward dynamic PAAm hydrogels with on‐demand control over hydrogel properties as well as electrically conductive PAAm hydrogels for bioelectronics. Polyacrylamide (PAAm) hydrogels are versatile soft substrates commonly used in cell‐material studies. This Review explores their fabrication, physico‐chemical properties, and modification strategies to incorporate features like 2D patterns, surface topographies, and mechanical stiffness gradients. Additionally, recent advances in photoresponsive and electrically conductive PAAm hydrogels for bioelectronics are discussed.

Mechanical properties are one of the most important characteristics of biomaterials for many different applications, including biomedicine. Soft biomaterials, such as hydrogels, are difficult to characterize by conventional mechanical testing, because their mechanical properties are much lower than required by conventional testing machines. In this work, we aimed to systematically study the mechanical behavior of a model soft material, polyacrylamide hydrogels, under different loading modes: tension, torsion, compression, and indentation. This allowed us to develop a comprehensive approach to the mechanical testing of soft materials. To overcome excessive compression and slippage of the hydrogel samples when fixed in the grips during tension, additional 3D-printed grips were designed. Digital image correlation was used to determine the Poisson’s ratio of the hydrogels. The Young’s modulus values obtained from all types of mechanical tests analyzed were highly correlated. However, for hydrogels with a low crosslinker concentration, 1–2%, tension–compression asymmetry was observed. Moreover, the results of the mechanical tests were verified in indentation tests, including analytical estimation, and full-scale and numerical experiments. We also discuss the limits of using a two-parameter Mooney–Rivlin model for fitting hydrogel uniaxial tension deformation curves, which was unstable for the hydrogels with 4 and 9% crosslinker concentration. The implemented approach provided a comprehensive analysis of the mechanical behavior of biomaterials. The elastic moduli for all hydrogels studied were in the range from 20 to 160 kPa, which corresponds well to human soft tissues, making them a promising material for application as tissue-mimicking phantoms.

Biofunctionalized polyacrylamide (PAAm) hydrogels are important 2D substrates for studying cell physics and mechanobiology. In this work, an arylmethylsulfone (MS) comonomer is developed that can be incorporated into PAAm gels under aqueous radical polymerization conditions. The resulting hydrogels show similar properties to unmodified PAAm gels, indicating that the comonomer is incorporated without affecting PAAm physical properties. The MS‐containing PAAm hydrogels allow efficient conjugation of thiol derivatized biomolecules and require very low comonomer content (2 mM, 0.18 mol% relative to AAm) and thiol incubation amounts (≥ 0.15 µg per gel) to achieve functional densities that elicit cell responses. Compared to carboxyl‐functionalized PAAm hydrogels, a 10‐fold lower comonomer concentration and a 10‐fold lower ligand feed concentration are sufficient to achieve comparable cell adhesion responses. The new comonomer opens up possibilities for efficient and straightforward biofunctionalization of PAAm hydrogels used in cell biophysical studies. A new methylsulfone comonomer is presented that can be integrated into polyacrylamide hydrogels for efficient biofunctionalization with thiol‐bearing ligands. Very low comonomer and ligand incubation amounts are required to achieve ligand densities that elicit cell responses, offering an efficient pathway to bioactive hydrogel surfaces for cell physics and mechanobiology studies.

Following the general aim of recapitulating the native mechanical properties of tissues and organs in vitro, the field of materials science and engineering has benefited from recent progress in developing compliant substrates with physical and chemical properties similar to those of biological materials. In particular, in the field of mechanobiology, soft hydrogels can now reproduce the precise range of stiffnesses of healthy and pathological tissues to study the mechanisms behind cell responses to mechanics. However, it was shown that biological tissues are not only elastic but also relax at different timescales. Cells can, indeed, perceive this dissipation and actually need it because it is a critical signal integrated with other signals to define adhesion, spreading and even more complicated functions. The mechanical characterization of hydrogels used in mechanobiology is, however, commonly limited to the elastic stiffness (Young’s modulus) and this value is known to depend greatly on the measurement conditions that are rarely reported in great detail. Here, we report that a simple relaxation test performed under well-defined conditions can provide all the necessary information for characterizing soft materials mechanically, by fitting the dissipation behavior with a generalized Maxwell model (GMM). The simple method was validated using soft polyacrylamide hydrogels and proved to be very useful to readily unveil precise mechanical properties of gels that cells can sense and offer a set of characteristic values that can be compared with what is typically reported from microindentation tests.

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.

In this study, a novel calcium phosphate/polyacrylamide copolymer/α-type hemihydrate gypsum (CPO/PAM/α-HHG) composite material was prepared by polymerising a stable inorganic CPO precursor, end-capped with triethylamine (TEA), with an organic polyacrylamide (PAM) hydrogel to form a CPO/PAM precursor solution. Subsequently, this precursor solution was mixed with inorganic α-hemihydrate gypsum. The effects of CPO/PAM precursor addition and CPO addition on the slurry flowability, initial setting time, and mechanical properties of hardened specimens of the CPO/PAM/α-HHG composite were investigated. The structural characteristics of the composites were analysed by XRD, FE-SEM, and TGA. The results show that the initial setting time of the CPO/PAM/α-HHG composites was 26.7 min, which was 140.5% longer than that of the pure water α-HHG system and 3.9% longer than that of the PAM/α-HHG system; additionally, the oven-dried specimens had a flexural strength of 27.59 MPa and a compressive strength of 68.48 MPa, which were 77.2% and 102.0% higher than those of the pure water α-HHG system and 38.8% and 14.1% higher than those of the PAM/α-HHG system, respectively. The wet compressive strength of the CPO/PAM/α-HHG composites was improved by 11.8% compared to that of the PAM/α-HHG system. A structural analysis showed that CPO promoted the gelation process of PAM and allowed the hydration reaction process of α-HHG to be fully carried out by slowing down the gelation process of the organic network, which led to the full development of both organic and inorganic networks, ultimately forming an interspersed inorganic/organic dual-network structure, which enhanced the comprehensive mechanical properties of the composites. This study provides a new idea for the modification of α-type hemihydrate gypsum and a new method for the preparation of high-utilisation and high-performance gypsum-based composites.

Wound healing is a biological process that involves a series of consecutive process, and its impairment can lead to chronic wounds and various complications. Recently, there has been a growing interest in employing nanotechnology to enhance wound healing. Silver nanoparticles (AgNPs) have expanded significant attention due to their wide range of applications in the medical field. The advantages of AgNPs include their easy synthesis, change their shape, and high surface area. Silver nanoparticles are very efficient for topical drug administration and wound healing because of their high ratio of surface area to volume. The efficiency of AgNPs depends on the synthesis method and the intended application. Green synthesis methods offer an eco-friendly approach by utilizing natural sources such as plant extracts and fungus. The characterization of nanoparticles plays an important character, and it is accomplished through the use of several characterization methods such as UV-Vis spectroscopy, Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD). These techniques are employed to confirm the specific characters of the prepared Silver Nanoparticles. Additionally, the review addresses the challenges and future perspectives of utilizing green-synthesized AgNPs loaded in Polyacrylamide hydrogel for wound healing applications, including the optimization of nanoparticle size, and release kinetics. Overall, this review highlights the potential of green-synthesized AgNPs loaded in Polyacrylamide hydrogel as promising for advanced wound healing therapies. There are different approaches of usage of AgNPs for wound healing such as polyacrylamide -hydrogels, and the mechanism after their antibacterial action, have been exposed.

Background Polyacrylamide hydrogel (PAHG) is a new biomaterial that emerged in the last century and has been widely used in human filler procedures, such as injectable breast augmentation and facial contour improvement. However, as the implantation time of the material increases, various complications have been reported, which reflects that the safety of this material has not been adequately studied. Therefore, a more in-depth experimental analysis becomes particularly important. Methods We collected lesion tissues from six patients with PAHG facial injection. The lesion tissues were examined histologically and molecularly. Results Complications caused by PAHG facial injection included pain, subcutaneous nodules, swelling and gel displacement. Western blot revealed decreased expression of neural tissue markers, and increased expression of macrophage markers and oxidative stress-related factors. The results of this study provide new insights into the mechanism and development of PAHG facial injection complications. Conclusion This report explores the possible mechanism of PAHG complications after facial injection from a new perspective of oxidative stress and inflammation for the first time, which provides a reference for researchers and clinicians to further understand the characteristics of materials and strictly control surgical indications to reduce complications. No Level Assigned This journal requires that authors assign a level of evidence to each submission to which Evidence-Based Medicine rankings are applicable. This excludes Review Articles, Book Reviews, and manuscripts that concern Basic Science, Animal Studies, Cadaver Studies, and Experimental Studies. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Hybrid composites of gold nanoparticles (Au NPs) with polymer hydrogels are promising platforms for the development of new materials that can respond to external stimuli (chemical, physical, mechanical), reversibly absorb/release water and reagents, act as plasmonic sensors, and also as catalysts for photochemical processes and photothermal actuators of micromechanical processes. We proposed a one-step synthesis of a hybrid composite of Au NPs doped into polyacrylamide (PAAm) hydrogel by reducing HAuCl 4 with acrylamide (AAm) and simultaneous radical polymerization of AAm, initiated by (NH 4 ) 2 S 2 O 8 , in the aqueous solution. The influence of initial concentrations of 0.26–10 mM Au and 0.1–1 M AAm on the morphology and structure of Au NPs, as well as on the phase stability of the products, was studied. At concentrations of 3 mM Au, 1 M AAm and 1.2 mM (NH 4 ) 2 S 2 O 8 , а temperature of 60 °C and a heating time of 6 h, a stable product with a clearly defined SPR band with a maximum at 552 nm was obtained. It contained polycrystalline Au NPs in the form of spheroids, cuboctahedra, and rods up to ~100 nm size. The product was used to obtain plasmonic films of Au NPs-PAAm composite after drying at 100 °C and gold after thermal removal of the polymer matrix at 550 °C.The work used UV-visible and photon correlation spectroscopy, X-ray diffraction, synchronous thermal analysis, transmission and scanning electron microscopy. Graphical Abstract Highlights A hybrid composite of gold nanoparticles with polyacrylamide hydrogel was synthesized by a one-pot, one-step method from H[AuCl 4 ] and acrylamide. Optimal conditions for the synthesis of a stable product are initial concentrations of 3 mM for gold and 1 M for acrylamide, temperature 60 °C. Using a composite hydrogel on glass, films of a dry composite of gold nanoparticles with polyacrylamide were obtained by dehydration at 100 °C and thin gold after heating at 550 °C. Surface plasmon resonance bands in the spectra of the synthesized hybrid composite hydrogel and of films have favorable for use in optical sensing well-defined maxima in the wavelength range 570–600 nm.

Introduction and hypothesis To assess quality of life (QoL) and sexual function outcomes at 3 years after tension-free vaginal tape (TVT) and polyacrylamide hydrogel injection (PAHG) for stress urinary incontinence (SUI). Methods In this randomized trial comparing TVT ( n  = 104) and PAHG ( n  = 108), we assessed changes in QoL and sexuality using the Urogenital Distress Inventory (UDI-6), Incontinence Impact Questionnaire, Short Form (IIQ-7), Pelvic Organ Prolapse/Urinary Incontinence Sexual Questionnaire (PISQ-12) and RAND-36 Item Health Survey (RAND-36) at baseline and at 3 years. This is a secondary analysis of a randomized, noninferiority trial comparing patient satisfaction after TVT and PAHG. Results In both groups, incontinence-related QoL improved from the baseline ( p  < 0.00), except for difficulty emptying the bladder and pain/discomfort. Total scores of UDI-6 and IIIQ-7 were lower for TVT compared to PAHG ( p  < 0.00) indicating better QoL at 3 years. Urinary incontinence with sexual activity or fear of incontinence restricting sexual activity improved in both groups ( p  < 0.00), with higher scores for physical section subscale in PISQ-12 ( p  = 0.02) for TVT. Physical and social functioning (RAND-36) improved from the baseline in both groups ( p  < 0.01) with a better outcome in the TVT group for physical functioning ( p  = 0.00). Conclusions Both TVT and PAHG improve QoL and sexual function in primary SUI with better incontinence and health-related QoL scores in the TVT group compared to the PAHG group at 3 years.