Biodegradable nanostructures: Degradation process and biocompatibility of iron oxide nanostructured arrays

Iron oxide nanoparticle-based nanocomposites in biomedical application

Iron-oxide-based biomagnetic nanocomposites, recognized for their significant properties, have been utilized in MRI and cancer treatment for several decades. The expansion of clinical applications is limited by the occurrence of adverse effects. These limitations are largely attributed to suboptimal material design, resulting in agglomeration, reduced magnetic relaxivity, and inadequate functionality. To address these challenges, various synthesis methods and modification strategies have been used to tailor the size, shape, and properties of iron oxide nanoparticle (FeONP)-based nanocomposites. The resulting modified nanocomposites exhibit significant potential for application in diagnostic, therapeutic, and theranostic contexts, including MRI, drug delivery, and anticancer and antimicrobial activity. Yet, their biosafety profile must be rigorously evaluated. Such efforts will facilitate the broader clinical translation of FeONP-based nanocomposites in biomedical applications.

3D Printing Assisted Fabrication of Copper-Silver Mesoporous Bioactive Glass Nanoparticles Reinforced Sodium Alginate/Poly(vinyl alcohol) Based Composite Scaffolds: Designed for Skin Tissue Engineering

Additive manufacturing (also known as 3D printing) is a promising method for producing patient-specific implants. In the present study, sodium alginate (Na-ALG)/poly(vinyl alcohol) (PVA) polymer blends of varying ratios (1:0, 3:1, 1:1, and 1:3) were used to produce tailored-designed skin scaffolds using a 3D bioprinter. Samples of skin scaffolds were printed at 20 layers with a layer height of 0.15 mm using a needle with an inner diameter of 330 μm while maintaining the extrusion speed, extrusion width, and fill density at 10 mm/s, 0.2 mm, and 85%, respectively. The Na-ALG/PVA blend with a 3:1 ratio showed the best printability due to its good viscosity and minimal nozzle leakage, allowing for the fabrication of skin scaffolds with high fidelity and the desired morphological characteristics. Then, copper-silver doped mesoporous bioactive glass nanoparticles (Cu-Ag MBGNs) were incorporated into the Na-ALG/PVA blend (which had already been prepared by using a Na-ALG:PVA ratio of 3:1) in order to obtain therapeutic (angiogenic and antibacterial) effects. The fabricated Na-ALG/PVA/Cu-Ag MBGNs biocomposite scaffolds with dimensions of 20 mm× 20 × 3 mm3 and pore size of 400 ± 60 μm exhibited a promising fidelity. The presence of chemical bonds attributed to Na-ALG, PVA, and Cu-Ag MBGNs and the uniform distribution of Na, C, and O elements within the microstructure of the scaffolds were confirmed by EDX, SEM, and FTIR analyses. The scaffolds were hydrophilic and exhibited proper swelling and degradation behavior for skin tissue engineering. According to the inhibition halo test, the scaffolds exhibited strong antibacterial activity against Staphylococcus aureus and Escherichia coli. The cytocompatibility to human-derived fibroblast cells was confirmed by the WST-8 assay and in vivo Chorioallantoic Membrane Assay. In addition, Na-ALG/PVA/Cu-Ag MBGNs showed angiogenic potential, exhibiting favorable wound healing properties.

Nanomaterial-based contrast agents

Medical imaging, which empowers the detection of physiological and pathological processes within living subjects, has a vital role in both preclinical and clinical diagnostics. Contrast agents are often needed to accompany anatomical data with functional information or to provide phenotyping of the disease in question. Many newly emerging contrast agents are based on nanomaterials as their high payloads, unique physicochemical properties, improved sensitivity and multimodality capacity are highly desired for many advanced forms of bioimaging techniques and applications. Here, we review the developments in the field of nanomaterial-based contrast agents. We outline important nanomaterial design considerations and discuss the effect on their physicochemical attributes, contrast properties and biological behaviour. We also describe commonly used approaches for formulating, functionalizing and characterizing these nanomaterials. Key applications are highlighted by categorizing nanomaterials on the basis of their X-ray, magnetic, nuclear, optical and/or photoacoustic contrast properties. Finally, we offer our perspectives on current challenges and emerging research topics as well as expectations for future advancements in the field.

Stimuli-Responsive Silica Silanol Conjugates: Strategic Nanoarchitectonics in Targeted Drug Delivery

The design of novel drug delivery systems is exceptionally critical in disease treatments. Among the existing drug delivery systems, mesoporous silica nanoparticles (MSNs) have shown profuse promise owing to their structural stability, tunable morphologies/sizes, and ability to load different payload chemistry. Significantly, the presence of surface silanol groups enables functionalization with relevant drugs, imaging, and targeting agents, promoting their utility and popularity among researchers. Stimuli-responsive silanol conjugates have been developed as a novel, more effective way to conjugate, deliver, and release therapeutic drugs on demand and precisely to the selected location. Therefore, it is urgent to summarize the current understanding and the surface silanols' role in making MSN a versatile drug delivery platform. This review provides an analytical understanding of the surface silanols, chemistry, identification methods, and their property-performance correlation. The chemistry involved in converting surface silanols to a stimuli-responsive silica delivery system by endogenous/exogenous stimuli, including pH, redox potential, temperature, and hypoxia, is discussed in depth. Different chemistries for converting surface silanols to stimuli-responsive bonds are discussed in the context of drug delivery. The critical discussion is culminated by outlining the challenges in identifying silanols' role and overcoming the limitations in synthesizing stimuli-responsive mesoporous silica-based drug delivery systems.

Co-assembling of natural drug-food homologous molecule into composite hydrogel for accelerating diabetic wound healing

Diabetic wound healing is a major clinical challenge due to its vulnerability to bacterial infection and the prolonged inflammation in the wound. Traditional dressings for the healing of diabetic wounds are often suffered from unsatisfactory efficacy and frequent dressing changes which may cause secondary damage. Therefore, it is necessary to find a wound dressing that balances material functionality, degradation, safety, and tissue regeneration. Our recent studies demonstrated that gallic acid (GA) could spontaneously form supramolecular hydrogels at a relatively high concentration. However, a single network of GA hydrogel is prone to degradation, poor adhesion, and poor swelling, and may not be suitable for wound healing dressings. In this study, a composite hydrogel (GAK) was constructed by introducing konjac glucomannan (KGM) into the gel system of gallic acid (GA) and applied to promote diabetic wound healing. The composite hydrogel (GAK) with superior surface adhesion, stability, and swelling properties than the single-network of GA hydrogel. Moreover, in vitro experiments showed that GAK hydrogel had excellent biocompatibility and exhibited antibacterial activity against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). Additionally, the GAK hydrogel could significantly accelerate angiogenesis, collagen deposition, and re-epithelialization during wound healing in diabetic mice, reducing the expression of related inflammatory proteins interleukin-1β (IL-1β), tumor necrosis factor-alpha (TNF-α), and cyclooxygenase-2 (COX-2), and improving the wound closure rate. The findings of this study suggest that this composite hydrogel (GAK) can be an ideal dressing material for accelerating diabetic wound healing.

Modifications on porous absorbable Fe-based scaffolds for bone applications: A review from corrosion and biocompatibility viewpoints

Iron (Fe) and Fe-based scaffolds have become a research frontier in absorbable materials which is inherent to their promising mechanical properties including fatigue strength and ductility. Nevertheless, their slow corrosion rate and low biocompatibility have been their major obstacles to be applied in clinical applications. Over the last decade, various modifications on porous Fe-based scaffolds have been performed to ameliorate both properties encompassing surface coating, microstructural alteration via alloying, and advanced topologically order structural design produced by additive manufacturing (AM) techniques. The recent advent of AM produces topologically ordered porous Fe-based structures with an optimized architecture having controllable pore size and strut thickness, intricate internal design, and larger exposed surface area. This undoubtedly opens up new options for controlling Fe corrosion and its structural strengths. However, the in vitro biocompatibility of the AM porous Fe still needs to be addressed considering its higher corrosion rate due to the larger exposed surface area. This review summarizes the latest progress of the modifications on porous Fe-based scaffolds with a specific focus on their responses on the corrosion behavior and biocompatibility.

Insight into the bioabsorption of Fe-based materials and their current developments in bone applications

Iron (Fe) and Fe-based materials have been vigorously explored in orthopedic applications in the past decade mainly owing to their promising mechanical properties including high yield strength, elastic modulus and ductility. Nevertheless, their corrosion products and low corrosion kinetics are the major concerns that need to be improved further despite their appealing mechanical strengths. The current studies on porous Fe-based scaffolds show an improved corrosion rate but the in vitro biocompatibility is still problematic in general. Unlike the Mg implants, the biodegradation and bioabsorption of Fe-based implants are still not well described. This vague issue could implicate the development of Fe-based materials as potential medical implants as they have not reached the clinical trial stage yet. Thus, there is a need to understand in-depth the Fe corrosion behavior and its bioabsorption mechanism to facilitate the material design of Fe-based scaffolds and further improve its biocompatibility. This manuscript provides an important insight into the basic bioabsorption of the multi-ranged Fe-based corrosion products with a review of the latest progress on the corrosion & in vitro biocompatibility of porous Fe-based scaffolds together with the remaining challenges and the perspective on the future direction.

Magnetic 3D scaffolds for tissue engineering applications: bioactive glass (45S5) coated with iron-loaded hydroxyapatite nanoparticles

Magnetic 45S5 bioactive glass (BG) based scaffolds covered with iron-loaded hydroxyapatite (Fe-HA-BG) nanoparticles were obtained and its cytotoxicity investigated. Fe-HA nanoparticles were synthesized by a wet chemical method involving the simultaneous addition of Fe²⁺/Fe³⁺ions. BG based scaffolds were prepared by the foam replica procedure and covered with Fe-HA by dip-coating. Fe-HA-BG magnetic saturation values of 0.049 emu g^-1and a very low remanent magnetization of 0.01 emu g^-1were observed. The mineralization assay in simulated body fluid following Kokubo's protocol indicated that Fe-HA-BG scaffolds exhibited improved hydroxyapatite formation in comparison to uncoated scaffolds at shorter immersion times. The biocompatibility of the materialin vitrowas assessed using human osteoblast-like MG-63 cell cultures and mouse bone marrow-derived stroma cell line ST-2. Overall, the results herein discussed suggest that magnetic Fe-HA coatings seem to enhance the biological performance of 45S5 BG based scaffolds. Thus, this magnetic Fe-HA coated scaffold is an interesting system for bone tissue engineering applications and warrant further investigation.

Biocompatibility and Biological Performance Evaluation of Additive-Manufactured Bioabsorbable Iron-Based Porous Suture Anchor in a Rabbit Model

This study evaluated the biocompatibility and biological performance of novel additive-manufactured bioabsorbable iron-based porous suture anchors (iron_SAs). Two types of bioabsorbable iron_SAs, with double- and triple-helical structures (iron_SA_2_helix and iron_SA_3_helix, respectively), were compared with the synthetic polymer-based bioabsorbable suture anchor (polymer_SAs). An in vitro mechanical test, MTT assay, and scanning electron microscope (SEM) analysis were performed. An in vivo animal study was also performed. The three types of suture anchors were randomly implanted in the outer cortex of the lateral femoral condyle. The ultimate in vitro pullout strength of the iron_SA_3_helix group was significantly higher than the iron_SA_2_helix and polymer_SA groups. The MTT assay findings demonstrated no significant cytotoxicity, and the SEM analysis showed cells attachment on implant surface. The ultimate failure load of the iron_SA_3_helix group was significantly higher than that of the polymer_SA group. The micro-CT analysis indicated the iron_SA_3_helix group showed a higher bone volume fraction (BV/TV) after surgery. Moreover, both iron SAs underwent degradation with time. Iron_SAs with triple-helical threads and a porous structure demonstrated better mechanical strength and high biocompatibility after short-term implantation. The combined advantages of the mechanical superiority of the iron metal and the possibility of absorption after implantation make the iron_SA a suitable candidate for further development.

Synthesis, Characterization, Antibacterial Properties, and In Vitro Studies of Selenium and Strontium Co-Substituted Hydroxyapatite

In this study, as a measure to enhance the antimicrobial activity of biomaterials, the selenium ions have been substituted into hydroxyapatite (HA) at different concentration levels. To balance the potential cytotoxic effects of selenite ions (SeO32-) in HA, strontium (Sr2+) was co-substituted at the same concentration. Selenium and strontium-substituted hydroxyapatites (Se-Sr-HA) at equal molar ratios of x Se/(Se + P) and x Sr/(Sr + Ca) at (x = 0, 0.01, 0.03, 0.05, 0.1, and 0.2) were synthesized via the wet precipitation route and sintered at 900 °C. The effect of the two-ion concentration on morphology, surface charge, composition, antibacterial ability, and cell viability were studied. X-ray diffraction verified the phase purity and confirmed the substitution of selenium and strontium ions. Acellular in vitro bioactivity tests revealed that Se-Sr-HA was highly bioactive compared to pure HA. Se-Sr-HA samples showed excellent antibacterial activity against both Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus carnosus) bacterial strains. In vitro cell-material interaction, using human osteosarcoma cells MG-63 studied by WST-8 assay, showed that Se-HA has a cytotoxic effect; however, the co-substitution of strontium in Se-HA offsets the negative impact of selenium and enhanced the biological properties of HA. Hence, the prepared samples are a suitable choice for antibacterial coatings and bone filler applications.

Designing Better Cardiovascular Stent Materials - A Learning Curve

Cardiovascular stents are life-saving devices and one of the top 10 medical breakthroughs of the 21st century. Decades of research and clinical trials have taught us about the effects of material (metal or polymer), design (geometry, strut thickness, and the number of connectors), and drug-elution on vasculature mechanics, hemocompatibility, biocompatibility, and patient health. Recently developed novel bioresorbable stents are intended to overcome common issues of chronic inflammation, in-stent restenosis, and stent thrombosis associated with permanent stents, but there is still much to learn. Increased knowledge and advanced methods in material processing have led to new stent formulations aimed at improving the performance of their predecessors but often comes with potential tradeoffs. This review aims to discuss the advantages and disadvantages of stent material interactions with the host within five areas of contrasting characteristics, such as 1) metal or polymer, 2) bioresorbable or permanent, 3) drug elution or no drug elution, 4) bare or surface-modified, and 5) self-expanding or balloon-expanding perspectives, as they relate to pre-clinical and clinical outcomes and concludes with directions for future studies.

Degradation Resistance and In Vitro Cytocompatibility of Iron-Containing Coatings Developed on WE43 Magnesium Alloy by Micro-Arc Oxidation

Iron (Fe) is an important trace element for life and plays vital functions in maintaining human health. In order to simultaneously endow magnesium alloy with good degradation resistance, improved cytocompatibility, and the proper Fe amount for the body accompanied with degradation of Mg alloy, Fe-containing ceramic coatings were fabricated on WE43 Mg alloy by micro-arc oxidation (MAO) in a nearly neutral pH solution with added 0, 6, 12, and 18 g/L ferric sodium ethylenediaminetetraacetate (NaFeY). The results show that compared with the bare Mg alloy, the MAO samples with developed Fe-containing ceramic coatings significantly improve the degradation resistance and in vitro cytocompatibility. Fe in anodic coatings is mainly present as Fe2O3. The increased NaFeY concentration favorably contributes to the enhancement of Fe content but is harmful to the degradation resistance of MAO coatings. Our study reveals that the developed Fe-containing MAO coating on Mg alloy exhibits potential in clinical applications.

Superiority of L-tartaric Acid Modified Chiral Mesoporous Silica Nanoparticle as a Drug Carrier: Structure, Wettability, Degradation, Bio-Adhesion and Biocompatibility

PURPOSE

The purpose of this research was to study the basic physicochemical and biological properties regarding the application of L-tartaric acid modified chiral mesoporous silica nanoparticle (CMSN) as a drug carrier, and to explore the structure-property relationship of silica-based materials.

METHODS

CMSN with functions of carboxyl modification and chirality was successfully synthesized through co-condensation method, and the basic characteristics of CMSN, including morphology, structure, wettability, degradation, bio-adhesion and retention ability in gastrointestinal tract (GI tract) were estimated by comparing with non-functionalized mesoporous silica nanoparticles (MSN). Meanwhile, the biocompatibility and toxicity of L-tartaric modification were systematically evaluated both in vitro and in vivo through MTT cell viability assay, cell cycle and apoptosis assay, hemolysis assay, histopathology examination, hematology analysis, and clinical chemistry examination.

RESULTS

CMSN and MSN were spherical nanoparticles with uniform mesoporous structure. CMSN with smaller pore size and carboxyl functional groups exhibited better wettability. Besides, CMSN and MSN could dissolve thoroughly in simulated physiological fluids during a degradation period of 1-12 weeks. Interestingly, the in vitro and in vivo behaviors of carriers, including degradation, bio-adhesion and retention ability in the GI tract were closely related to wettability. As expected, CMSN had faster degradation rate, higher mucosa-adhesion ability, and longer retention time. Particularly, CMSN improved the bio-adhesion property in both gastric mucosa and small intestinal mucosa, and prolonged the GI tract retention time to at least 12 h, which meant higher probability for absorption. The biocompatibility and toxicity examination indicated that CMSN was a kind of biocompatible bio-material with good blood compatibility and negligible toxicity, which is required for further applications in biological fields.

CONCLUSION

CMSN with functions of carboxyl modification and chirality had superiority in terms of both physicochemical and biological properties. The in vitro and in vivo behaviors of carriers, including degradation, bio-adhesion, and retention were closely related to wettability.

Corrosion Resistance of Anodic Layers Grown on 304L Stainless Steel at Different Anodizing Times and Stirring Speeds

Different chemical and physical treatments have been used to improve the properties and functionalities of steels. Anodizing is one of the most promising treatments, due to its versatility and easy industrial implementation. It allows the growth of nanoestructured oxide films with interesting properties able to be employed in different industrial sectors. The present work studies the influence of the anodizing time (15, 30, 45 and 60 min), as well as the stirring speed (0, 200, 400, and 600 rpm), on the morphology and the corrosion resistance of the anodic layers grown in 304L stainless steel. The anodic layers were characterized morphologically, compositionally, and electrochemically, in order to determine the influence of the anodization parameters on their corrosion behavior in a 0.6 mol L−1 NaCl solution. The results show that at 45 and 60 min anodizing times, the formation of two microstructures is favored, associated with the collapse of the nanoporous structures at the metal-oxide interphace. However, both the stirring speed and the anodizing time have a negligeable effect on the corrosion behavior of the anodized 304L SS samples, since their electrochemical values are similar to those of the non-anodized ones.