Study of Manipulative In Situ Pore-Formation upon Polymeric Coating on Cylindrical Substrate for Sustained Drug Delivery.

Herein, the micro-porous polylactic acid coating applied on the surface of the cylindrical substrate is fabricated by a novel in situ pore-formation strategy based on the combinational effect of breath figure (BF) and vapor-induced phase separation (VIPS) processes. Under the condition of high environmental humidity, solvent pair of chloroform and dimethylformamide is employed for post-treatment onto pre-formed PLA coating to induce the pore-formation following the mechanism of BF and VIPS, respectively. A composite porous structure with both cellular-like and bi-continuous network morphologies is obtained. By tunning the experimental factors including the ratio of the solvent pair, environmental humidity, and temperature, morphological manipulation upon the pore morphology can be facilely achieved based on the control of mechanism transition between BF and VIPS. Paclitaxel is used as a model drug and loaded into the porous coating by the wicking effect of post-immersion. Coatings with different morphological features show varying drug loading and release capacities. The 28-day release test reveals dynamic release profiles between different coating samples, with the total release rate ranging from 35.70% to 79.96%. Optimal loading capacity of 19.28 µg cm-2 and 28-day release rate of 35.70% are achieved for the coating with composite BF-VIPS structure. This research established a cost-efficient strategy with high flexibility in the structural manipulation concerning the construction of drug-eluting coating with the feature of manipulative drug delivery.

Increased stability of short femoral stem through customized distribution of coefficient of friction in porous coating.

Stress shielding and aseptic loosening are complications of short stem total hip arthroplasty, which may lead to hardware failure. Stems with increased porosity toward the distal end were discovered to be effective in reducing stress shielding, however, there is a lack of research on optimized porous distribution in stem's coating. This study aimed to optimize the distribution of the coefficient of friction of a metaphyseal femoral stem, aiming for reducing stress shielding in the proximal area. A finite element analysis model of an implanted, titanium alloy short-tapered wedge stem featuring a porous coating made of titanium was designed to simulate a static structural analysis of the femoral stem's behavior under axial loading in Analysis System Mechanical Software. For computational feasibility, 500 combinations of coefficients of friction were randomly sampled. Increased strains in proximal femur were found in 8.4% of the models, which had decreased coefficients of friction in middle medial areas of porous coating and increased in lateral proximal and lateral and medial distal areas. This study reported the importance of the interface between bone and middle medial and distal lateral areas of the porous coating in influencing the biomechanical behavior of the proximal femur, and potentially reducing stress shielding.

Femoral stem taper geometry and porous coating in cementless direct anterior primary total hip arthroplasty.

Objective: This study aims to compare the clinical outcomes and complications between a fully coated, dual-tapered hip stem versus a proximally coated, triple-tapered hip stem in patients undergoing cementless direct anterior (DA) primary total hip arthroplasty (THA). Methods: A retrospective analysis was conducted on patients who underwent primary THA with either a fully coated, dual-tapered hip stem or a proximally coated, triple-tapered stem with at least a 1-year follow up. Exclusion criteria included any patients that did not receive either femoral stem, those undergoing bilateral THA, those with a surgical approach other than DA, those with an indication other than osteoarthritis, avascular necrosis (AVN), or femoral neck fracture, and those that had a cemented femoral component. Complications and clinical outcomes were assessed. Statistical analyses were conducted to identify significant differences between the groups. Results: A total of 95 patients were included in the study. The average ages for the dual-tapered and triple-tapered stem cohorts were 63.6 and 59.5, respectively (p = 0.168). At 1-year follow-up, no significant differences were seen between the groups in terms of ambulatory status, ROM, and patient satisfaction (p = 0.414, p = 0.106, and p = 0.126). 6 (18 %) of the patients receiving the dual-tapered, fully coated hip stem had at least one complication while 8 (13 %) of the triple-tapered, proximally coated hip stem patients did (p = 0.550). Conclusion: Both hip stem cohorts demonstrated comparable clinical outcomes and complication rates in patients undergoing primary DA THA and we believe that either hip stem may be a reasonable choice for patients. Future studies with larger sample sizes and longer follow-up periods are warranted to validate these findings.

Combined Porous-Monolithic TiNi Materials Surface-Modified with Electron Beam for New-Generation Rib Endoprostheses.

TiNi alloys are very widely used materials in implant fabrication. When applied in rib replacement, they are required to be manufactured as combined porous-monolithic structures, ideally with a thin, porous part well-adhered to its monolithic substrate. Additionally, good biocompatibility, high corrosion resistance and mechanical durability are also highly demanded. So far, all these parameters have not been achieved in one material, which is why an active search in the field is still underway. In the present study, we prepared new porous-monolithic TiNi materials by sintering a TiNi powder (0-100 µm) on monolithic TiNi plates, followed by surface modification with a high-current pulsed electron beam. The obtained materials were evaluated by a set of surface and phase analysis methods, after which their corrosion resistance and biocompatibility (hemolysis, cytotoxicity, and cell viability) were evaluated. Finally, cell growth tests were conducted. In comparison with flat TiNi monoliths, the newly developed materials were found to have better corrosion resistance, also demonstrating good biocompatibility and potential for cell growth on their surface. Thus, the newly developed porous-on-monolith TiNi materials with different surface porosity and morphology showed promise as potential new-generation implants for use in rib endoprostheses.

Fabrication and Experimental Study of Micro/Sub-Micro Porous Copper Coating for Anti-Icing Application.

Micro and sub-micro-spherical copper powder slurries were elaborately prepared to fabricate different types of porous coating surfaces. These surfaces were further treated with low surface energy modification to obtain the superhydrophobic and slippery capacity. The surface wettability and chemical component were measured. The results showed that both the micro and sub-micro porous coating layer greatly increased the water-repellence capability of the substrate compared with the bare copper plate. Notably, the PFDTES-fluorinated coating surfaces yielded superhydrophobic ability against water under 0 °C with a contact angle of ~150° and a contact angle of hysteresis of ~7°. The contact angle results showed that the water repellency of the coating surface deteriorated with decreasing temperature from 10 °C to -20 °C, and the reason was probably recognized as the vapor condensation in the sub-cooled porous layer. The anti-icing test showed that the ice adhesion strengths of the micro and sub-micro-coated surfaces were 38.5 kPa and 30.2 kPa, producing a 62.8% and 72.7% decrease compared to the bare plate. The PFDTES-fluorinated and slippery liquid-infused porous coating surfaces both produced ultra-low ice adhesion strengths of 11.5-15.7 kPa compared with the other non-treated surfaces, which showed prominent properties for anti-icing and deicing requirement of the metallic surface.

Light- and Field-Controlled Diffusion, Ejection, Flow and Collection of Liquid at a Nanoporous Liquid Crystal Membrane.

Liquid manipulation at solid surfaces has attracted plenty of interest yet most of them are limited to one or two direction(s), while transport in three dimensions is largely unexplored. Here, we demonstrate three-dimensionally steered dynamic liquid mobility at nanoporous liquid crystal polymer coatings. To this end, we orchestrate liquid motion via sequential triggers of light and/or electric field. Upon a primary flood exposure to UV light, liquid is ejected globally over the entire coating surfaces. We further reallocate the secreted liquid by applying a secondary electric field stimulus. By doing so, the liquid is transported and collected at pre-set positions as determined by the electrode positions. We further monitor this process in real-time and perform precise analysis. Interestingly, when applying those two triggers simultaneously, we discover a UV-gated liquid-release effect, which decreases threshold voltage as well as threshold frequency.

Efficient synthesis of N-acetyllactosamine using immobilized ß-galactosidase on a novel 3D polymer support.

A novel polymer support was prepared by curing of epoxy resin in ethanol solution in the macropores of a melamine sponge. The produced polymer gel could uniformly deposit on the surface of melamine in either porous or nonporous morphology. The composite sponge with porous coating can be used as a large-sized and well-mass transferred support for the immobilization of ß-galactosidase from Bacillus circulans through method of adsorption and crosslinking, and a column reactor was made for the preparation of N-acetyllactosamine in a sealed circulation way. The porosity and specific surface area of the support were 91.6 % and 46 m2/g, respectively. The loading amount and the specific activity of immobilized ß-galactosidase under the optimal immobilization conditions were 41.2 mg/gsupport and 16.5 U/mgprotein, respectively. In the biosynthesis of N-acetyllactosamine lactose and N-acetylglucosamine were used as donor and acceptor, respectively. Under optimized conditions the N-acetyllactosamine yield reached 54 % within 150 min at 50 °C. After 10 cycles, the immobilized ß-galactosidase retained 70 % of the original activity.

Multiplexed Covalent Patterns on Double-Reactive Porous Coating.

We have conceptualized and demonstrated an approach based on the combination of hydrophobicity, a substrate-independent dip coating as porous material with double residual chemical reactivities for implementing multiplexed, miniaturized and unclonable bulk-infused patterns of different fluorophores following distinct reaction pathways. The embedded hydrophobicity (∼102°) restricted the unwanted spreading of beaded aqueous ink on the coating. The constructions of micropatterns on porous dip-coating via ink-jet printing or microchannel cantilever spotting offered orthogonal read-out and remained readable even after removal of the exterior of the coating.

Irregular porous titanium enhances implant stability and bone ingrowth in an intra-articular ovine model.

Two commercially available porous coatings, Gription and Porocoat, were compared for the first time in a challenging intra-articular, weight-bearing, ovine model. Gription has evolved from Porocoat and has higher porosity, coefficient of friction, and microtextured topography, which are expected to enhance bone ingrowth. Cylindrical implants were press-fit into the weight-bearing regions of ovine femoral condyles and bone ingrowth and fixation strength evaluated 4, 8, and 16 weeks postoperatively. Biomechanical push-out tests were performed on lateral femoral condyles (LFCs) to evaluate the strength of the bone-implant interface. Bone ingrowth was assessed in medial femoral condyles (MFCs) as well as implants retrieved from LFCs following biomechanical testing using backscattered electron microscopy and histology. By 16 weeks, Gription-coated implants exhibited higher force (2455 ± 1362 vs. 1002 ± 1466 N; p = 0.046) and stress (12.60 ± 6.99 vs. 5.14 ± 7.53 MPa; p = 0.046) at failure, and trended towards higher stiffness (11,510 ± 7645 vs. 5010 ± 8374 N/mm; p = 0.061) and modulus of elasticity (591 ± 392 vs. 256 ± 431 MPa; p = 0.061). A strong, positive correlation was detected between bone ingrowth in LFC implants and failure force (r = 0.93, p < 10-13 ). By 16 weeks, bone ingrowth in Gription-coated implants in MFCs was 10.50 ± 6.31% compared to 5.88 ± 2.77% in Porocoat (p = 0.095). Observations of the bone-implant interface, made following push-out testing, showed more bony material consistently adhered to Gription compared to Porocoat at all three time points. Gription provided superior fixation strength and bone ingrowth by 16 weeks.

Influence of strut-size and cell-size variations on porous Ti6Al4V structures for load-bearing implants.

Mechanical properties of porous metal coatings in load-bearing implants play a critical role in determining the in vivo lifetime. However, there is a knowledge gap in measuring the shear strength of porous metal coatings at the porous-dense interface. This study evaluated pore morphology dependence and strut-size on compression, shear deformation, and in vitro response of additively manufactured porous Ti6Al4V structures. Selective laser melting (SLM)-based additive manufacturing (AM) technique was used to process two types of structures with honeycomb cell design-one with constant cell-size of ∼470 µm with mean strut-size varying from 92 to 134 µm, and denoted as strut-size variation (SSV); and the other with a constant strut-size of ∼135 µm with mean cell-size varying from 580 to 740 µm, denoted as cell-size variation (CSV). It was observed that under compressive loading, changes in elastic modulus were more sensitive to variations in strut-size over cell-size. Under shear loading at the porous-dense interface, strength enhancement and material hardening were observed in both SSV and CSV samples due to pore-collapsing. Our results show that for hexagonal cell designs, shear behavior is more sensitive to variations in cell-size over strut-size, although elastic modulus is more sensitive to changes in strut-size for porous metallic structures. From in vitro hFOB analysis, it was observed that pore size of 670 µm demonstrated the highest osteoblast cell viability among porous structures with evidence of pore-bridging by cells. P. aeruginosa bacterial culture showed that bacterial cell viability was higher for porous structures than dense Ti, with evidence of pore-bridging by bacterial cells.

Fabrication of Porous Aluminum Coating by Cored Wire Arc Spray for Anchoring Antifouling Hydrogel Layer.

Biofouling has been persisting as a worldwide problem due to the difficulties in finding efficient environment-friendly antifouling coatings for long-term applications. Developing novel coatings with desired antifouling properties has been one of the research goals for surface coating community. Recently hydrogel coating was proposed to serve as antifouling layer, for it offers the advantages of the ease of incorporating green biocides, and resisting attachment of microorganisms by its soft surface. Yet poor adhesion of the hydrogel on steel surfaces is a big concern. In this study, porous matrix aluminum coatings were fabricated by cored wire arc spray, and the sizes of the pores in the aluminum (Al) coatings were controlled by altering the size of the cored powder of sodium chloride. Silicone hydrogel was further deposited on the porous coating. The hydrogel penetrated into the open pores of the porous Al coatings, and the porous Al structure significantly enhanced the adhesion of the hydrogel. In addition, hydrogel coating exhibited very encouraging antifouling properties.

Preparation of a composite coating film via vapor induced phase separation for air purification and real-time bacteria photocatalytic inactivation.

Infectious diseases resulted from transmitting of bacteria or virus like COVID-19 via air-borne droplets have brought severe threat to human beings worldwide. Cutting the spreading paths to obtain clean air is one of the promising strategies to prevent people from such dangerous diseases. In this work, we have employed a strategy of spray coating in combination with vapor induced phase separation to prepare a composite coating film to fulfill that purpose. A stable mixture suspension containing micelles of block copolymer of poly(styrene-block-butadiene-block-styrene) and TiO2 nanoparticles was sprayed onto stainless steel mesh to evaporate solvent in non-solvent vapor atmospheres. A water vapor atmosphere and an ethanol vapor atmosphere were in turn employed to improve the mechanical strength of the obtained coating film. The porous microstructure, the porosity, and the superhydrophobicity of the coating film were carefully characterized and analyzed. The air pressure-drop of the coating film was determined to be lower than 100 Pa, indicating a high air permeability. Moreover, a foggy air containing E. coli was pressed through the coating film via a home-made apparatus to simulate the air purification system, where E. coli contained air-borne droplets were intercepted by the film matrix in a physical manner, and the bacteria was photocatalytically inactivated at the meantime. A filtration efficiency of 99.7% and a 99.6% efficiency of real-time photocatalytic inactivation of E. coli demonstrate the promising potential of the coating film.

A hafnium oxide-coated dendrite-free zinc anode for rechargeable aqueous zinc-ion batteries.

In aqueous zinc-ion batteries, metallic zinc is widely used as an anode because of its non-toxicity, environmental benignity, low cost, high abundance and theoretical capacity. However, growth of zinc dendrites, corrosion of zinc anode, passivation, and occurrence of side reactions during continuous charge-discharge cycling hinder development of zinc-ion batteries. In this study, a simple strategy involving application of a HfO2 coating was used to guide uniform deposition of Zn2+ to suppress formation of zinc dendrites. The HfO2-coated zinc anode improves electrochemical performance compared with bare Zn anode. Therefore, for zinc-zinc symmetric cells, zinc anode with HfO2 coating (48 mV) shows lower voltage hysteresis than that of bare Zn anode (63 mV) at a current density of 0.4 mA cm-2. Moreover, cell with HfO2 coating also shows good cycling performance in Zn-MnO2 full cells. At a constant current density of 1.0 A g-1, discharge capacity of bare Zn-MnO2 full cell is only 37.9 mAh g-1 after 500 cycles, while that of Zn@HfO2-MnO2 full cell is up to 78.3 mAh g-1. This good electrochemical performance may be the result of confinement effect and reduction of side reactions. Overall, a simple and beneficial strategy for future development of rechargeable aqueous zinc-ion batteries is provided.

Long-Term Outcomes for Cementless Anatomic Femoral Components, Compared by Area of Porous Coating, in Patients Younger Than 50 Years Treated for Hip Dysplasia.

BACKGROUND: We investigated whether the proximal circumferential porous coating of cementless stems would make implant survival of >20 years possible in young patients. METHODS: Data for patients younger than 50 years with hip dysplasia who had an anatomic stem implanted with a proximal porous coating with hydroxyapatite/tricalcium phosphate were reviewed. Noncircumferential porous (non-C-type) stems were used in 17 hips (13 cases), and circumferential porous (C-type) stems were used in 87 hips (68 cases). Acetabular components with conventional polyethylene were used for all hips. The mean ages at surgery for patients with non-C-type stems and those with C-type stems were 43.3 and 44.7 years, respectively. Stems that had not loosened were retained at the time of acetabular revision. The average duration of follow-up for patients with non-C-type stems was 26.9 years and was 22.3 years for those with C-type stems. RESULTS: Mean survival rates as determined by the Kaplan-Meier method were 74.9% at 20 years and 59.9% at 25 years for non-C-type stems and were 100% at 20 years and 94.0% at 25 years for C-type stems. The survivorship for C-type stems was significantly higher than that for non-C-type stems (P < .01). Focal osteolysis in the shoulder of 37 hips with C-type stems suppressed the spread of osteolysis to the distal femur. CONCLUSION: Anatomic femoral stems with a circumferential porous coating provide excellent durability in patients with hip dysplasia who are 50 years of age or younger. LEVEL OF EVIDENCE: Therapeutic Level IV.

Flexible Daytime Radiative Cooling Enhanced by Enabling Three-Phase Composites with Scattering Interfaces between Silica Microspheres and Hierarchical Porous Coatings.

Daytime radiative cooling has attracted considerable attention recently due to its tremendous potential for passively exploiting the coldness of the universe as clean and renewable energy. Many advanced materials with novel photonic micro/nanostructures have already been developed to enable highly efficient daytime radiative coolers, among which the flexible hierarchical porous coatings (HPCs) are a more distinguished category. However, it is still hard to precisely control the size distribution of the randomized pores within the HPCs, usually resulting in a deficient solar reflection at the near-infrared optical regime under diverse fabrication conditions of the coatings. We report here a three-phase (i.e., air pore-phase, microsphere-phase, and polymer-phase) self-assembled hybrid porous composite coating, which dramatically increases the average solar reflectance and yields remarkable temperature drops of ∼10 and ∼ 30 °C compared to the ambient circumstance and black paint, respectively, according to the rooftop measurements. Mie theory and Monte Carlo simulations reveal the origin of the low reflectivity of as-prepared two-phase porous HPCs, and the optical cooling improvement of the three-phase porous composite coatings is attributed to the newly generated interfaces possessing the high scattering efficiency between the hierarchical pores and silica microspheres hybridized with appropriate mass fractions. As a result, the hybrid porous composite approach enhances the whole performance of the coatings, which provides a promising alternative to the flexible daytime radiative cooler.

Revision of Acetabular Component with a Debonded Porous Coating in an Elderly Patient.

Debonding of the porous coating from the acetabular component of a total hip endoprosthesis is a rare complication. Revision total hip arthroplasty for an unstable acetabular component with a debonded porous coating strongly fixed to the bone can be challenging, especially in elderly patients of poor overall health. In such patients, revision procedures should be as simple and safe as possible. We present our technique of solving that problem in a case of an 82-year-old female with bad general condition and unstable acetabular component of hip endoprosthesis. Because of extremely deficient bone stock, a well-fixed porous coating was left in acetabulum to serve as a "cage", allowing cemented acetabular component placement. This procedure can reduce the risk of intraoperative bone fracture, blood loss, and duration of surgery, which is important in elderly patients with poor overall health.

Osteo-Compatibility of 3D Titanium Porous Coating Applied by Direct Energy Deposition (DED) for a Cementless Total Knee Arthroplasty Implant: in Vitro and in Vivo Study.

: Direct energy deposition (DED) technology has gained increasing attention as a new implant surface technology that replicates the porous structure of natural bones facilitating osteoblast colonization and bone ingrowth. However, concerns have arisen over osteolysis or chronic inflammation that could be caused by Cobalt-chrome (CoCr) alloy and Titanium (Ti) nanoparticles produced during the fabrication process. Here, we evaluated whether a DED Ti-coated on CoCr alloy could improve osteoblast colonization and osseointegration in vitro and in vivo without causing any significant side effects. Three types of implant CoCr surfaces (smooth, sand-blasted and DED Ti-coated) were tested and compared. Three cell proliferation markers and six inflammatory cytokine markers were measured using SaOS2 osteoblast cells. Subsequently, X-ray and bone histomorphometric analyses were performed after implantation into rabbit femur. There were no differences between the DED group and positive control in cytokine assays. However, in the 5-bromo-2'-deoxyuridine (BrdU) assay the DED group exhibited even higher values than the positive control. For bone histomorphometry, DED was significantly superior within the 1000 µm bone area. The results suggest that DED Ti-coated metal printing does not affect the osteoblast viability or impair osseointegration in vitro and in vivo. Thus, this technology is biocompatible for coating the surfaces of cementless total knee arthroplasty (TKA) implants.

Titanium Porous Coating Using 3D Direct Energy Deposition (DED) Printing for Cementless TKA Implants: Does It Induce Chronic Inflammation?

Because of the recent technological advances, the cementless total knee arthroplasty (TKA) implant showed satisfactory implant survival rate. Newly developed 3D printing direct energy deposition (DED) has superior resistance to abrasion as compared to traditional methods. However, there is still concern about the mechanical stability and the risk of osteolysis by the titanium (Ti) nanoparticles. Therefore, in this work, we investigated whether DED Ti-coated cobalt-chrome (CoCr) alloys induce chronic inflammation reactions through in vitro and in vivo models. We studied three types of implant surfaces (smooth, sand-blasted, and DED Ti-coated) to compare their inflammatory reaction. We conducted the in vitro effect of specimens using the cell counting kit-8 (CCK-8) assay and an inflammatory cytokine assay. Subsequently, in vivo analysis of the immune profiling, cytokine assay, and histomorphometric evaluation using C57BL/6 mice were performed. There were no significant differences in the CCK-8 assay, the cytokine assay, and the immune profiling assay. Moreover, there were no difference for semi-quantitative histomorphometry analysis at 4 and 8 weeks among the sham, smooth, and DED Ti-coated samples. These results suggest that DED Ti-coated printing technique do not induce chronic inflammation both in vitro and in vivo. It has biocompatibility for being used as a surface coating of TKA implant.

Bone ingrowth comparison of irregular titanium and cobalt-chromium coatings in a translational cancellous bone model.

The use of cobalt-chromium (CoCr)-bearing surfaces in total joint replacement (TJR) remains the predominate bearing surface. The conundrum with using this biomaterial has been selecting an ideal porous coating to assure reproducible skeletal attachment. There has been evidence that smooth CoCr beads may be inferior for skeletal attachment compared to identically shaped titanium (Ti) beads. Recent in vitro studies have demonstrated that an increased surface area and roughness favors osteoblast adhesion to metallic biomaterials. Therefore, we hypothesized that an irregular shape CoCr bead with an increased surface texture would help correct the negative bone responses that have been reported with smooth beaded CoCr coatings and thus allowing for bone ingrowth equivalently as an irregular commercially pure Ti porous coating with similar porosity. This investigation employed a weight-bearing translational sheep cancellous bone model to accurately simulate a cancellous bone response as it would be clinically in a human TJR. The data analyses obtained from this investigation revealed similar bone responses between the porous coatings. By 12 weeks the irregular shape CoCr coating was able to achieve similar bone ingrowth with skeletal interlock when compared to a clinically proven Ti porous coating.

Surface functionalization on nanoparticles via atomic layer deposition.

As an ultrathin film preparation method, atomic layer deposition (ALD) has recently found versatile applications in fields beyond semiconductors, such as energy, environment, catalysis and so on. The design, preparation and characterization of thin film applied in the emerging fields have attracted great interests. The development of ALD technique on particles opens up a broad horizon in the advanced nanofabrication. Pioneering applications are exploring conformal coating, porous coating and selective surface modification of nanoparticles. Conformal encapsulation of particles is a major application to protect materials with ultrathin films from being eroded by the external environment while keeping the original properties of the primary particles. Porous coating has been developed to simultaneously expose the particles' surface and provide nanopores, which is another important method that demonstrates its advantages in modification of electrode materials, catalysis and energy applications, etc. Selective ALD takes the method forward in order to precisely control the directionality of decoration sites on the particles and selectively passivate undesired facets, sites, or defects. Such methods provide practical strategies for atomic scale and precise surface functionalization on particles and greatly expand its potential applications.