Wall Surface Research Articles

Impact of various heat sources on the transient heat transfer rate in a 3D cylinder consisting of parts with different thermal conductivity coefficients

Numerical analysis of time-dependent conductive heat transfer in three-dimensional solid bodies with a heat source is important in their use in various industries. In this article, an attempt has been made to investigate this issue for a cylinder consisting of four equal pieces with different thermal conductivity coefficients and heat sources, and conclusions have been drawn. The geometry of the cylinder consists of two lower (first) and upper (second) layers. In the lower layer of two solid bodies, one is a piece of rubber with a thermal conductivity coefficient of K1=0.16 w/m○k and the other is a piece of walnut wood with a thermal conductivity coefficient of K2=0.077 w/m○k and two solid objects are used in the upper layer. One is a piece of polyurethane with a thermal conductivity coefficient of K3=0.02 w/m○k and the other is a piece of cork with a thermal conductivity coefficient of K4=0.04 w/m○k. There are four heat source mechanisms: constant value, linear, quadratic, and sinusoidal or periodic heat source with a certain frequency. All the surfaces of the cylinder walls in the time interval 0 ≤ t ≤ 10 s10, T=0 are assumed. The obtained results show that the temperature distribution when the value of the heat source is constant affects a larger area, and the highest increase in temperature in the direction of the z-axis belongs to the constant, quadratic, sinusoidal and linear heat source, respectively.

Novel modular PCM wall board for building heating energy efficiency: Material preparation, manufacture and dynamic thermal testing

With the comprehensive implementation of China’s “dual carbon” goals, the building heating sector, characterized by high energy consumption and emissions, urgently requires low-carbon transformation. However, energy-saving measures for plateau regions are scarce and face challenges due to harsh climates. This study proposes an innovative heating method utilizing composite phase change materials. A new modular phase change thermal storage electric heating terminal integrated with a photovoltaic thermal system has been designed to address issues of high building energy consumption and problems related to heating system freezing and leakage in the Tibetan Plateau (Qinghai-Xizang Plateau). Laboratory tests were conducted on six groups of samples with different structures and placements to examine their heat storage and release characteristics. Results indicate: The system’s temperature stabilization time totals 14.6 h; Horizontally placing the terminal reduces melting time by up to 2.7 h, enhancing heat storage performance; Structure three shortens solidification time by up to 2.2 h compared to structure one, improving heat release performance; Vertically placed terminals have better heat release performance than horizontally placed ones, resulting in more effective indoor heating. This study proposes a modular design for phase change heat storage electric heating walls, simplifying installation and maintenance while maintaining aesthetic appeal. Detailed temperature measurements of different wall surfaces revealed excellent cyclic heat storage and release performance. The developed phase change heat storage electric heating terminal is expected to significantly reduce heating energy consumption in the Tibetan Plateau (Qinghai-Xizang Plateau), enhancing building energy efficiency and providing valuable insights for further applications of phase change materials in building design.

Thermal criticality and two-step diffusion-reaction of electromagnetic Casson-Williamson fluid flow along a vertical channel with convective cooling under bimolecular kinetic

The need to examine diverse conditions involving industrial working fluids and improving thermal transfer efficiency cannot be overstated. Every thermal system must monitor and control excessive heat production and propagation to avert disruptions in various engineering processes. Therefore, the study investigated the theoretical significance of thermal criticality and a two-step exothermic reaction on Casson-Williamson fluid dynamics behaviour through a fixed vertical channel driven by an electromagnetic field, axial pressure gradient, and heat buoyancy force under a generalized bimolecular chemical kinetic. The heat exchange at the convective wall surface is adhered to Newton’s law of cooling. The Galerkin weighted residual method (GWRM) was utilized to solve the dimensionless nonlinear equations governing the flow within the boundary layer, yielding graphical representations of momentum and energy distributions. The results show that higher values of the activation energy, Frank-Kamenetskii parameter, electric field loading, activation ratio term, Weissenberg number, and second step term led to better heat dispersion and, eventually, complete combustion of hydrocarbons in the Casson-Williamson fluid. To avoid system disruptions, the study underscores the crucial need for continuous monitoring of all factors that stimulate internal heat generation to prevent system failures, emphasizing the importance of vigilance in the field of thermal systems.

Study on the daily thermal radiation iso-disturbance on a building by trees in summer

Many studies have demonstrated that the cooling and energy-saving effects of planting trees around buildings vary depending on their location. However, most research has focused on a limited number of representative planting sites. This study evaluates the reduction in thermal radiation absorbed by walls over a single day due to trees, defined as daily thermal radiation disturbance (TRDD). Using a combination of experiments and ENVI-met software simulations, we established a coordinate system to map the TRDD distribution of trees at various locations around a building. The findings reveal that trees at different locations exhibit isoTRDD lines, which are symmetrical about the building’s centerline. Trees planted along these isoTRDD lines exert equal effects on TRDD. The isoTRDD lines form a series of ellipses that decay in two stages with increasing distance between the tree crowns and the walls (DW-T): rapid decay when DW-T is less than 3 m and slower decay beyond 3 m. Additionally, we found a linear positive correlation between the change in the sky view factor (ΔSVF) on the wall surface caused by trees and the TRDD. Trees near the north and south walls, as well as those along the building's diagonal, primarily block sky-scattered radiation (R²>0.97). Trees around the east and west walls block both sky-scattered and direct solar short-wave radiation (R²>0.85). This indicates a significant relationship between isoTRDD and SVF of the building. The methodology proposed in this study allows for a comprehensive assessment of the spatial evolution of TRDD for trees around the building, providing a scientific basis for the spatial design of trees to optimize cooling and energy savings. Moreover, the relationship between ΔSVF and TRDD enables rapid calculations and comparisons of the cooling effects of trees at different locations.

A defect detection network for painted wall surfaces based on YOLOv5 enhanced by attention mechanism and bi-directional FPN

A defect detection network for painted wall surfaces based on YOLOv5 enhanced by attention mechanism and bi-directional FPN

The Jajarkot Earthquake: Revealed the Vulnerability of Load Bearing Structures in Western Nepal

The Jajarkot Earthquake, which occurred on 3rd November, 2023 of magnitude 5.7 (Mw) exposed Nepal’s longstanding vulnerability to seismic activity. This paper presents damage assessments derived from both on-site field observations and secondary resources to evaluate the damages sustained by load bearing masonry structures. In the region, 95% of the building structures are based on masonry construction. The damage status of structures in Jajarkot and Rukum East highlighted that about 50% of the building structures were partially and complete damage. The evaluation encompassed various aspects, including the types, mechanisms, and underlying causes of the damage incurred by structures. The observed damage was categorized using an established catalogue originally developed for the identification of failure mechanisms and vulnerability assessment. The common types of damage encompassed features like cracks in the load bearing external walls and corners, diagonal cracks originating from door and window corners, vertical out-of-plane displacement of external walls, collapse of external walls, and partial collapse of load bearing internal walls, fracturing of window and door lintels and complete collapse of structure. Some special forms of damage which was of new nature and distinct from those observed in prior seismic events such as the Gorkha earthquake included ruptures in the outer surfaces of loadbearing external walls, partial roof structure collapses, out-of-plane fragmentation or disintegration as well as rupture. The causes underlying this general damage were attributed to irregular bonding systems, weak mortar, stone block formation, size of stone blocks, absence of tie beams, weakly connected corners, insufficient connections of wall-roof and wall-floor systems, and differing internal wall systems. The mechanisms of damage varied based on the number and specifics of these causative factors, as well as certain structural attributes.

Caffeine Protects Keratinocytes from Trichophyton mentagrophytes Infection and Behaves as an Antidermatophytic Agent.

Caffeine affords several beneficial effects on human health, acting as an antioxidant, anti-inflammatory agent, and analgesic. Caffeine is widely used in cosmetics, but its antimicrobial activity has been scarcely explored, namely against skin infection agents. Dermatophytes are the most common fungal agents of human infection, mainly of skin infections. This work describes the in vitro effect of caffeine during keratinocyte infection by Trichophyton mentagrophytes, one of the most common dermatophytes. The results show that caffeine was endowed with antidermatophytic activity with a MIC, determined following the EUCAST standards, of 8 mM. Caffeine triggered a modification of the levels of two major components of the fungal cell wall, β-(1,3)-glucan and chitin. Caffeine also disturbed the ultrastructure of the fungal cells, particularly the cell wall surface and mitochondria, and autophagic-like structures were observed. During dermatophyte-human keratinocyte interactions, caffeine prevented the loss of viability of keratinocytes and delayed spore germination. Overall, this indicates that caffeine can act as a therapeutic and prophylactic agent for dermatophytosis.

Numerical assessment of hydrothermal and entropy generation characteristics of graphene quantum dots nanofluid in a microchannel heat sink incorporating secondary channels and ribs

Efficient heat dissipation from electronic chips is essential for enhancing their performance and longevity. Significant progress has been achieved through the introduction of nanofluids and microchannel heat sinks. However, there is still a need for nanofluids that demonstrate exceptional thermal properties and stability. Graphene quantum dots nanofluid, an innovative carbon-based coolant with zero-dimensional nanostructures, presents promising features such as excellent chemical stability, surfactant-free preparation, superior thermal properties, and minimal impact on rheological characteristics. This study explores, for the first time, the hydrothermal behavior and entropy generation of graphene quantum dots nanofluid in a microchannel heat sink comprising secondary flow channels and ribs. To this end, a three-dimensional conjugate heat transfer model is built using ANSYS Fluent software, and the governing equations are solved using the finite volume method. The simulations are carried out considering temperature-dependent thermophysical properties under different concentrations ranging from 0 to 0.5 % and Reynolds numbers ranging from 100 to 500. The results reveal that the maximum bottom wall surface temperature decreases by 5.88 K, while the heat transfer coefficient improves by 24.9 % compared to the base fluid. Moreover, the total entropy generation reduces by 14.7 %. On the other hand, the pressure drop increases by 43 %. Overall, the highest increment in Performance Evaluation Criteria is 10.8 % at a Reynolds number of 100 and a concentration of 0.5 %, making this particular condition suitable for practical applications.

Insight into the role of Streptococcus suis zinc metalloprotease C from the new serotype causing meningitis in piglets

Streptococcus suis (S. suis) is an important gram-positive pathogen and an emerging zoonotic pathogen that causes meningitis in swine and humans. Although several virulence factors have been characterized in S. suis, the underlying mechanisms of pathogenesis are not fully understood. In this study, we identified Zinc metalloproteinase C (ZmpC) probably as a critical virulence factor widely distributed in S. suis strains. ZmpC was identified as a critical facilitator in the development of bacterial meningitis, as evidenced by the detection of increased expression of TNF-α, IL-8, and matrix metalloprotease 9 (MMP-9). Subcellular localization analysis further revealed that ZmpC was localized to the cell wall surface and gelatin zymography analysis showed that ZmpC could cleave human MMP-9. Mice challenge demonstrated that ZmpC provided protection against S. suis CZ130302 (serotype Chz) and ZY05719 (serotype 2) infection. In conclusion, these results reveal that ZmpC plays an important role in promoting CZ130302 to cause mouse meningitis and may be a potential candidate for a S. suis CZ130302 vaccine.

Ion current rectification coupled with asymmetric temperature and surface charge in ultrashort conical nanopores

Ion current rectification (ICR) is one of the electrodynamic properties in asymmetric nanochannels, which has been utilized to develop biosensors, heavy metal ion detection, and ion diodes. Previous studies on ICR mainly focused on long nanopores (length >500 nm), and relatively few studies on ion rectification performance in short nanopores. Here, we use a finite element numerical solution to simulate the effect of coupling asymmetric temperature and surface charge distribution on the ion rectification performance of ultrashort conical nanopores (length = 100 nm). The results show that the ion rectification performance is significantly improved when the inner and outer surfaces of the nanopore are charged non-uniformly, which is more than three times that when the inner surface of the nanopore is charged non-uniformly or the outer surface is charged non-uniformly. In addition, the positive temperature difference enhances the ion enrichment and dissipation and improves the ion rectification performance of nanopores. On the contrary, negative temperature difference inhibits ion enrichment and dissipation in pores, which is not conducive to improving ion rectification performance. Abnormal behavior is observed for nanopores non-uniform charged only on the outer wall surface, where the negative temperature gradient enhances the accumulation and dissipation of ions within the pores, thereby increasing the rectification ratio. In addition, in order to more clearly understand the ion transport behavior in the ultrashort nanopore under asymmetric temperature conditions, we further investigated the influence of the tip radius of the nanopore, the solution volume concentration, and the charge type of each surface charge distribution on the ion current rectification performance. The results reveal the ion transport mechanism of ultrashort conical nanopores and provide practical guidance for designing and optimizing nanofluidic devices.

Investigation of heat transfer enhancement and thermal stratification phenomenon on supercritical hydrogen fuel flow

Thermal stratification is one of the major issues in rectangular regenerative cooling channels because of the asymmetric heating and limited turbulent diffusion of thermal energy of the fuel. As a result, the heat transfer performance is decreased. This paper uses Ansys fluent software to construct a novel cooling structure that combines wavy wall surfaces with cylindrical fins. In addition to this new configuration, this study also examined three other configurations (straight-smooth, cylindrical-ribs, and wavy-smooth) and compared them with each other. This structure aims to efficiently enhance hydrogen coolant flow and heat transfer characteristics while reducing the extent of the non-uniform distribution issue. The results show that the new structure’s Nusselt number and maximum wall temperature are enhanced by 46.89% and 22.71%, respectively, compared to the straight-smooth structure; in contrast, the friction factor increased only by 3.64% over the smooth channel. The novel design has the best thermal performance factor compared to the other three designs, which is improved by 43.33% over the smooth channel. Among all configurations, the new structure is the best fluid temperature distribution configuration, which shows an optimal distribution of the coolant temperatures between layers; thus, the stratification phenomena decreased significantly.

Functional ventilation building envelope integrated photovoltaic modules and phrase change material in subtropical climate: An in-depth numerical investigation

Most of existing solar ventilation envelope systems adopt a single structure including a glass cover a massive wall, which possesses the drawbacks of low thermal efficiency and poor stability. In recent decades, auxiliary power generation devices, led by photovoltaic (PV), have made epochal achievements in integrated building applications, while the superior thermal regulation capability of thermal storage materials, represented by phrase change materials (PCM), has further helped to improve the thermal environment of buildings, and the above two technologies have demonstrated great energy conservation potential. In order to explore the application and synergistic effect of the above two energy-conservation technologies in passive ventilation envelopes, a novel functional ventilation building envelope (FVBE) integrated with PV panel and PCM is proposed in this paper. A comprehensive exploration of the influence of various key parameters on the thermal performance of the FVBE-PV/PCM system. The electrical and thermal performance of the system is explored based on different seasonal climates. Specifically, effects of thickness as well as the melting temperature of PCM and the air channel width has been provided in this study. Taking the inner wall surface temperature (Tinner_wall), equivalent indoor load (Qload) and electrical efficiency (ηe) as evaluation indexes, the thermal efficiency, electrical performance and the coupling mechanism was assessed. Specifically, the coupling mechanism between the thermal performance and electrical performance of the FVBE-PV/PCM system was analyzed from the perspective of combined heat and power, revealing the functional characteristics of the system. Meanwhile, the article conducted a comparative study on the thermal and electrical performance of a typical building integrated PV (BIPV), FVBE-PV system FVBE-PV/PCM system. In particular, energy and exergy analysis is carried out to characterize the energy utilization of the FVBE-PV/PCM system in different structural systems. The research found that increasing the thickness of both the PCM and air channel leads to lower indoor temperature and heat flux, with different optimal phase transition temperatures for summer and winter. Although the FVBE-PV system exhibited a maximum 3.12 % reduction in power generation efficiency compared to the BIPV system due to increased PV temperature caused by air layer insulation, incorporating PCM can reduce exergy losses by an average of 31.731 % to mitigate this drawback and improve energy efficiency. Additionally, the analysis revealed varying coupling correlations between thermal performance and power generation based on two key parameters. This study could contribute to the functional improvement of the building envelope and simultaneous indoor thermal regulation.

Lattice boltzmann investigation of droplet interactions with non-uniform chemically patterned surfaces

In this study, we employed a non-orthogonal, three-dimensional, multi-relaxation-time pseudo-potential lattice Boltzmann method, and investigate the behaviors of droplets impacting chemically patterned surfaces. We considered two interfaces: a hydrophobic/neutral strip on a hydrophilic wall (surface A), and a hydrophilic strip on a hydrophobic wall (surface B). The dynamics of impact, including the evolution of the morphology and the droplet spreading factor, were investigated under the influence of the difference in wettability, Weber number (We), and strip width. An increase in the wettability difference of surface A delayed droplet detachment and reduced the amplitude of oscillations, where this can be attributed to the surface tension and viscous dissipation, which had more time to weaken the strength of the jet. The magnitude of droplet detachment time initially increased with We but eventually decreased. As We is further increased, the ratio of viscous loss to the initial kinetic energy of the droplet is decreased and resulted in a shorter detachment time. The unbalanced Young's force significantly affected the evolution of the droplet on surface B. The mass of the droplet accumulated near the borderline of the strip and expanded along the y-axis under the influence of the inertial force, where this led to a larger spreading factor along the y-axis. In addition, the mass of the droplet on the hydrophobic wall affected the strength of the unbalanced Young's force. As the strip width increased, the spreading factor initially increased but then decreased along the y-axis owing to the combined action of inertial forces.

Experimental Study on Heat Transfer Enhancement of 3D-Printed Mini Tubes Under Three Different Flow Directions

In this study, 864 heat transfer experimental data points and 216 pressure drop experimental data points were used to compare the heat transfer and friction factor behavior of 3D-printed and traditional tubes under uniform wall heat flux boundary condition. Experiments were conducted in the entire flow region that covers laminar, transition, and turbulent regions. The inside diameter of the test tubes is around 2 mm, and the average inside wall surface roughness for traditional and 3D-printed tubes is 2.211 μ m and 35.249 μ m , respectively. Comparing with the traditional tubes, in the upper transition and the turbulent regions, the Nusselt numbers and Colburn j -factors of the 3D-printed tube under three different flow directions were enhanced by an average of 52.67% and 51.59% respectively. The greater relative roughness of the 3D-printed tube enhanced the heat transfer but also increased the pressure drop significantly. The friction factors for the 3D-printed tube in these regions also increased by an average of 154.44% compared with the traditional tube. The results also show that the effect of different flow directions on heat transfer and pressure drop of the 3D-printed tube is insignificant relative to roughness. Moreover, the 3D-printed tube has an earlier transition compared with the traditional tube.

Development of a wheeled wall‐climbing robot with an internal corner wall adaptive magnetic adhesion mechanism

AbstractThe wall‐climbing robot is a growing trend for robotized intelligent manufacturing of large and complex components in shipbuilding, petrochemical, and other industries, while several challenges remain to be solved, namely, low payload‐to‐weight ratio, poor surface adaptability, and ineffective traversal maneuverability, especially on noncontinuous surfaces with internal corners (non‐CSIC). This paper designs a high payload‐to‐weight ratio wheeled wall‐climbing robot which can travel non‐CSIC effectively with a payload capacity of up to 75 kg, and it can carry a maximum load of 141.5 kg on a vertical wall. By introducing a semi‐enclosed magnetic adhesion mechanism, the robot preserves a redundant magnetic adsorption ability despite the occurrence of significant gaps between localized body components and the wall surface. In addition, by ingeniously engineering a passive adaptive module into the robot, both the surface adaptability and crossability are enhanced without increasing the gap between the body and the wall, thereby ensuring the optimization of the adsorption force. Considering the payload capacity and diversity when climbing on vertical walls, inclined walls, ceilings, and internal corner transitions, control equations for internal corner transitions and comprehensive simulations of magnetic adsorption forces are performed using FEA tools. Finally, a functional prototype was developed for rigorous experimental testing, with the results confirming that the robot successfully meets the desired functionality and performance benchmarks.

Experimental and numerical study of a novel composite building wall U-value

The present study aims to minimize the overall heat transfer coefficient (U-value) and heat flux through building walls to improve indoor thermal comfort, using different bricks and insulating materials in building wall construction. The building walls of three different types of bricks (Type-1, Type-2, and Type-3) were tested to compare the U-value through the wall. The brick with the low U-value was used to build a composite wall with the addition of glass wool and air cavity. The experiment was conducted maintaining different hot chamber temperatures (40℃ to 65℃) to see the effect of hot chamber temperature on the U-value. The temperature of the cold fluid chamber is increased by 0.9℃ in 0 to 210 min of testing duration. The maximum heat flux using Type-3 brick in the composite wall is reduced by 3.37%, and the percentage reduction in indoor temperature is 40.83%. Steady-state numerical analysis was also performed to perceive the temperature distribution on the composite wall surface and found to be well-matched with the experimental model with a percentage deviation of 1.96%. The results suggested that using glass wool and air cavities with low thermal conductivity, low density, and high specific heat capacity effectively reduces the U-value throughout the building wall.

Bayesian inversion for in-situ thermal characterisation of walls in the presence of thermal anomalies

This paper develops a Bayesian inverse modelling framework for the in-situ characterisation of walls' thermal performance in the presence of thermal anomalies subject to uncertainty. For any given wall, the proposed framework uses in-situ contact measurements of temperature and heat flux in order to approximate the (posterior) distribution of a set of parameters which are inputs of a 3D heat transfer model of the wall that accounts for the presence of unknown anomalies. The set of inputs that we infer include (i) the geometry of the thermal anomaly as well was its material properties, (ii) the as-built thermophysical properties of the clear part (i.e. without anomaly) of the wall (iii) surface resistances and (iv) modelling errors that arise from unaccounted sources of uncertainty in the boundary conditions. The geometry of the unknown thermal anomaly is parameterised with a level-set function that is inferred within the proposed Bayesian approach. In order to incorporate prior statistical information of the thermal anomaly, a Gaussian process conditioned on measurements from thermal images is employed to build a prior on the level-set function. The posterior distribution of inferred inputs is approximated via the implementation of an Ensemble Kalman Inversion algorithm that provides stable and accurate approximations of the posterior. This paper also proposes a methodology that uses the inferred 3D model to derive a thermally equivalent 1D model of the wall that is suitable for its integration with existing building energy performance software. The proposed inverse modelling technique is experimentally validated by characterising the thermal performance of an insulation panel in the presence of a thermal anomaly. Our computations show that the proposed approach produces a 3D model that accurately describes thermal performance, and a derived equivalent 1D model that effectively reproduces the dynamic thermal performance of the insulation panel in the presence of the thermal anomaly.

Long-Term Estimation of Depositions on Heating Surface During Boiling of Long-Life Coolant

Abstract Long-term boiling experiments with long-life coolant have been made with the aim to apply a boiling cooling technology to the next generation high exothermic electronic devices. The long-life coolant commonly used for cooling electronic devices is a mixture of ethylene glycol and water with multiple antirust inhibitors as additives, which may result in some depositions on the heat transfer surface during the boiling. In this study, the heat transfer surface made of copper was set vertically, and long-term experiments have been performed under the pool boiling. The deposition process was monitored for constant heating conditions. From experimental results, a distinct surface temperature change was observed under constant heat flux conditions. Just after keeping constant heat flux, the surface temperature increases with time, a certain time later decreases, and finally takes a stable value. During the temperature rise, the deposition adheres to the heat transfer surface in dots, which may cause an increase in thermal resistance between the wall surface and the working fluid. However, during the temperature drop, large growth of dot-like depositions on the heat transfer surface could alter wettability and surface roughness, enhancing boiling heat transfer. In addition, to investigate the characteristics of the depositions adhered to the heat transfer surface, a component analysis has been performed, which shows that the main substance was strontium hydroxyapatite, which might be formed by chemical reaction between components in the additives under the boiling.

Study on the Effect of a Sudden Jump in Wettability on Two-Component Liquid Flow in Sudden Contraction Devices.

This study experimentally investigated the effect of wettability and sudden changes in flow area on liquid-liquid extraction operation. The wall surface wettability has been altered by connecting the glass capillary (hydrophilic) and poly(tetrafluoroethylene) (PTFE)-coated capillary (hydrophobic) together in four different arrangements. In all of the arrangements, a 2 mm inner diameter tube of 35 cm length is used upstream, while a 1 mm inner diameter tube of 35 cm length is used downstream. Acetic acid mixed with toluene and water is used as a test fluid. Various flow patterns are observed: slug, droplet, slug with the droplet, and encapsulated drop in slug. The extraction efficiency is observed to be the maximum when the hydrophobic tube is used upstream, followed by a hydrophilic tube downstream. Due to the contraction effect, the specific surface area of the slug increases from 1.6 to 2.7 times. Further numerical simulations have been run using open CFD software OpenFoam to see the inner flow physics at the maximum efficiency due to a sudden jump in wettability. The presence of a recirculating zone downstream just after the plane of area change leads to the formation of encapsulated drop and enhances circulation within the slug.

In Vitro Biological Evaluation of an Alginate-Based Hydrogel Loaded with Rifampicin for Wound Care.

We report a biocompatible hydrogel dressing based on sodium alginate-grafted poly(N-vinylcaprolactam) prepared by encapsulation of Rifampicin as an antimicrobial drug and stabilizing the matrix through the repeated freeze-thawing method. The hydrogel structure and polymer-drug compatibility were confirmed by FTIR, and a series of hydrogen-bond-based interactions between alginate and Rifampicin were identified. A concentration of 0.69% Rifampicin was found in the polymeric matrix using HPLC analysis and spectrophotometric UV-Vis methods. The hydrogel's morphology was evaluated by scanning electron microscopy, and various sizes and shapes of pores, ranging from almost spherical geometries to irregular ones, with a smooth surface of the pore walls and high interconnectivity in the presence of the drug, were identified. The hydrogels are bioadhesive, and the adhesion strength increased after Rifampicin was encapsulated into the polymeric matrix, which suggests that these compositions are suitable for wound dressings. Antimicrobial activity against S. aureus and MRSA, with an increased effect in the presence of the drug, was also found in the newly prepared hydrogels. In vitro biological evaluation demonstrated the cytocompatibility of the hydrogels and their ability to stimulate cell multiplication and mutual cell communication. The in vitro scratch assay demonstrated the drug-loaded alginate-grafted poly(N-vinylcaprolactam) hydrogel's ability to stimulate cell migration and wound closure. All of these results suggest that the prepared hydrogels can be used as antimicrobial materials for wound healing and care applications.