Distribution, metabolism, excretion, and toxicity of implanted silver: a review

Association between Intestinal Flora Metabolites and Coronary Artery Vulnerable Plaque Characteristics in Coronary Heart Disease

Aims/Background The incidence of coronary heart disease (CHD) has been increasing annually. Patients with severe conditions may die from myocardial infarction, heart failure or malignant arrhythmia. Intestinal flora plays an important role in various metabolic processes, such as atherosclerosis, tumour formation, and inflammation. However, its direct role in promoting plaque vulnerability must be further explored and validated. Therefore, this study aims to explore the relationship between changes in intestinal flora, its metabolites in CHD patients and the vulnerability characteristics of coronary plaques. Methods This study recruited 180 subjects, among these, 90 CHD patients diagnosed between January 2023 and January 2024 were selected as the CHD group and 90 healthy volunteers were selected as the control group following a principle of 1:1 ratio. The differences in intestinal flora composition, metabolite levels, and blood biochemical indexes were compared between the two study groups. Based on the coronary angiography (CAG) and intravascular ultrasound (IVUS) results, the CHD group was divided into two sub-groups for stratified comparative analysis: the stable plaque group (n = 49) and the vulnerable plaque group (n = 41). Results The CHD group had reduced intestinal Bifidobacteria and lactic acid bacteria counts and higher intestinal Escherichia coli and Enterococcus levels than the control group (p < 0.05). Moreover, trimethylamine-N-oxide (TMAO) and phenylacetylglutamine (PAGln) levels were significantly higher in the CHD group compared to the control group (p < 0.05). Similarly, the CHD group exhibited substantially elevated serum triglyceride (TG), total cholesterol (TC), and low-density lipoprotein cholesterol (LDL-C) levels compared to the control group. However, compared to the control group, the high-density lipoprotein cholesterol (HDL-C) levels were significantly lower in the CHD group (p < 0.05). Furthermore, the serum levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), serum urea nitrogen (BUN), and serum creatinine (Scr) were comparable in the two experimental groups (p > 0.05). Similarly, intestinal Bifidobacteria, lactic acid bacteria, Escherichia coli, and Enterococcus compositions were comparable in CHD patients with vulnerable plaque and those with stable plaque (p > 0.05). Moreover, CHD patients with vulnerable plaque had elevated TMAO and PAGln levels than those with stable plaque (p < 0.05). However, TG, TC, HDL-C, LDL-C, ALT, AST, BUN, and Scr levels were comparable between CHD patients with a vulnerable plaque and those with stable plaque (p > 0.05). Multivariate regression analysis showed that diabetes, elevated TMAO levels, and elevated PAGln levels were potential risk factors for coronary plaque vulnerability (p < 0.05). Conclusion In summary, CHD patients exhibit significant intestinal flora imbalance, with elevated TMAO and PAGln metabolite levels, which are related to the characteristics of plaque instability.

Comparison of Efficacy and Safety between Two Silver-Containing Dressings in the Treatment of Deep Partial-Thickness Thermal Burns: A Multicenter, Double-Blind, Non-Inferiority, Randomized Clinical Trial

Aims/Background Silver-containing dressings are commonly utilized in burns treatment by virtue of their excellent antibacterial properties. Further research is needed to determine the type of silver-containing dressing that is more effective and safer for burns treatment. Pyperbranched polyamide-Ag dressing (HBPs-Ag dressing) is a modified polyamide dressing with a uniform coating of the Amino-terminated hyperbranched polymer (HBP-NH2)/Ag+ compound on its surface. This study aimed to evaluate the efficacy and safety of a silver ion-containing dressing (HBPs-Ag) for wound contact layer in the treatment of deep partial-thickness burns versus a silver-impregnated tulle dressing (Atrauman Ag). Methods This study was conducted between October 2019 to January 2021 at six sites in China. A total of 132 patients with deep partial-thickness burns (aged 18-65 years, injury occurring within 72 hours, burns <30% total burn surface area) were randomized 1:1 to HBPs-Ag group (study group) or Atrauman Ag group (control group). Data were obtained and analyzed, including total efficacy, wound healing rate, wound healing time, rate of negative bacterial culture from wound secretions, systemic response, skin or tissue irritation, local skin color changes, wound swelling, wound pain and adverse events. Results For partial thickness burns, the HBPs-Ag dressing was not inferior to Atrauman Ag dressing because the total efficiency of HBPs-Ag group (98.3%) was comparable to that of Atrauman Ag group (94.7%) (p > 0.05). There were no significant differences in efficacy, wound healing rate, wound healing time, and rate of negative bacterial culture from wound secretions between the two groups (p > 0.05). There were no statistical differences in all safety indicators tested between the two groups (p > 0.05). Silver was detected in the blood or urine of only 5 patients (3.79%). Conclusion The HBPs-Ag dressing was not inferior to Atrauman Ag dressing in deep partial-thickness burns treatment, with both of them showcasing comparable efficacy and safety. Clinical Trial Registration Chinese Clinical Trial Registry (ChiCTR2100049814).

Biokinetics of inhaled silver, gold, copper oxide, and zinc oxide nanoparticles: a review

The understanding of nanomaterial toxicity is aided by biokinetic information pointing to potential target organs. Silver (Ag), copper oxide (CuO), and zinc oxide (ZnO) are often referred to as soluble materials in the literature. In addition, data suggest gold (Au) nanoparticles to be soluble in the mammalian body. We identified inhalation studies on these materials and extracted data on physicochemical properties, organ distribution, and excretion. Silver and gold were retained in the lung for an extended period (>2,000 and >672 hours, respectively); copper initially increased in lung and then returned to baseline at ∼500 hours. Zinc increased in the lungs after short-term exposure to zinc oxide, but not after prolonged exposure. In blood, silver initially increased after inhalation but then gradually declined over ∼200 hours. Gold was elevated in the blood after exposure to 4, 7, 11, and 13 nm particles (but not particles of 20, 34, and 105 nm) and remained elevated for at least 672 hours after exposure to the 4 and 11 nm particles. Silver increased in the liver and spleen and was still present 2,000 hours post exposure. Gold was elevated in several organs, including the spleen and kidney, for more than 600 hours post exposure, indicating persistence in some organs. Both silver and gold were increased in the brain and olfactory bulb. Overall, we found no large differences in the biodistribution of the four nanomaterials but note that silver and gold were still increased in several organs at the last investigated post-exposure time points.

Macroporous coating of silver-doped hydroxyapatite/silica nanocomposite on dental implants by EDTA intermediate to improve osteogenesis, antibacterial, and corrosion behavior

Coating a titanium (Ti) implant with hydroxyapatite (HA) increases its bioactivity and biocompatibility. However, implant-related infections and biological corrosion have restricted the success of implant. To address these issues, a modified HA nanocomposite (HA/silica-EDTA-AgNPs nanocomposite) was proposed to take advantage of the sustained release of silver nanoparticles (AgNPs) and silicate ions through the silica-EDTA chelating network. As a result, a uniform layer of nanocomposite, compared to HA as the gold standard, was formed on Ti implants without fracture and with a high level of adhesion, using plasma electrolytic oxidation (PEO). Bioactivity assessment evidenced a shift in the surface phase of the Ti implant to generation of beta-tricalcium phosphate, a more bioresorbable material than HA. Metabolic activity assessments using human dental pulp stem cells revealed that Ti surfaces modified by the new nanocomposite are superior to bare and HA-modified Ti surfaces for cell attachment and proliferationin vitro. In addition, it successfully inhibited bacterial growth and induced osteogenesis on the implant surface. Finally, potentiodynamic polarization behavior of Ti implants before and after coating confirmed that a thick oxide interface layer on the modified Ti surface acts as an electrical barrier and protects the substrate layer from corrosion. Therefore, the HA/silica-EDTA/Ag nanocomposite presented here, compared to HA, can better coat Ti dental implants due to its good biocompatibility and osteoinductive activity, along with improved biological stability.

Enhancing wound healing with zinc and silver nanocomposites synthesized with β-lactoglobulin: antimicrobial properties, collagen deposition, and systemic effects in a C57BL/6J mouse model

This study explores the potential of zinc and silver nanocomposites, synthesized with β-lactoglobulin, a whey protein, in promoting wound healing, using the C57BL/6J mouse model. Our research is distinct in its dual focus: assessing the antimicrobial efficacy of these nanocomposites and their impact on wound healing processes. The antimicrobial properties were investigated through minimum inhibitory concentration (MIC) assessments and colony-forming unit (CFU) tests, providing insights into their effectiveness against wound-associated microorganisms. Notably, the formulation's effective antibacterial concentration did not exhibit toxicity to mouse fibroblasts. A key aspect of our methodology involved the use of a stereoscopic microscope for detailed monitoring of the wound closure process. Additionally, the distribution and potential systemic effects of the zinc and silver ions were analyzed using Inductively Coupled Plasma-Mass Spectrometry (ICP-MS). This analysis was crucial in evaluating metal ion absorption through the wound site and estimating any toxic effects on the body. Our findings are particularly significant in the field of regenerative medicine. Transmission electron microscopy (TEM) revealed that the tested nanocomposites notably enhanced collagen deposition, a vital component in the wound healing process. Furthermore, a reduction in glycogen levels in hepatocytes was observed following treatment with these metal-protein dressings. This novel finding warrants further investigation. Overall, our findings highlight the diverse roles of zinc and silver nanocomposites in wound healing. This study not only contributes to our understanding of metal-protein complexes in tissue regeneration but also opens new avenues for research into the delivery mechanisms of such treatments for hard-to-heal wounds.

An In Vitro Study on the Application of Silver-Doped Platelet-Rich Plasma in the Prevention of Post-Implant-Associated Infections

Implant therapy is a common treatment option in dentistry and orthopedics, but its application is often associated with an increased risk of microbial contamination of the implant surfaces that cause bone tissue impairment. This study aims to develop two silver-enriched platelet-rich plasma (PRP) multifunctional scaffolds active at the same time in preventing implant-associated infections and stimulating bone regeneration. Commercial silver lactate (L) and newly synthesized silver deoxycholate:β-Cyclodextrin (B), were studied in vitro. Initially, the antimicrobial activity of the two silver soluble forms and the PRP enriched with the two silver forms has been studied on microbial planktonic cells. At the same time, the biocompatibility of silver-enriched PRPs has been assessed by an MTT test on human primary osteoblasts (hOBs). Afterwards, an investigation was conducted to evaluate the activity of selected concentrations and forms of silver-enriched PRPs in inhibiting microbial biofilm formation and stimulating hOB differentiation. PRP-L (0.3 µg/mm2) and PRP-B (0.2 µg/mm2) counteract Staphylococcus aureus, Staphylococcus epidermidis and Candida albicans planktonic cell growth and biofilm formation, preserving hOB viability without interfering with their differentiation capability. Overall, the results obtained suggest that L- and B-enriched PRPs represent a promising preventive strategy against biofilm-related implant infections and demonstrate a new silver formulation that, together with increasing fibrin binding protecting silver in truncated cone-shaped cyclic oligosaccharides, achieved comparable inhibitory results on prokaryotic cells at a lower concentration.

Self-promoted electroactive biomimetic mineralized scaffolds for bacteria-infected bone regeneration

Infected bone defects are a major challenge in orthopedic treatment. Native bone tissue possesses an endogenous electroactive interface that induces stem cell differentiation and inhibits bacterial adhesion and activity. However, traditional bone substitutes have difficulty in reconstructing the electrical environment of bone. In this study, we develop a self-promoted electroactive mineralized scaffold (sp-EMS) that generates weak currents via spontaneous electrochemical reactions to activate voltage-gated Ca2+ channels, enhance adenosine triphosphate-induced actin remodeling, and ultimately achieve osteogenic differentiation of mesenchymal stem cells by activating the BMP2/Smad5 pathway. Furthermore, we show that the electroactive interface provided by the sp-EMS inhibits bacterial adhesion and activity via electrochemical products and concomitantly generated reactive oxygen species. We find that the osteogenic and antibacterial dual functions of the sp-EMS depend on its self-promoting electrical stimulation. We demonstrate that in vivo, the sp-EMS achieves complete or nearly complete in situ infected bone healing, from a rat calvarial defect model with single bacterial infection, to a rabbit open alveolar bone defect model and a beagle dog vertical bone defect model with the complex oral bacterial microenvironment. This translational study demonstrates that the electroactive bone graft presents a promising therapeutic platform for complex defect repair.

Engineering 3D-Printed Advanced Healthcare Materials for Periprosthetic Joint Infections

The use of additive manufacturing or 3D printing in biomedicine has experienced fast growth in the last few years, becoming a promising tool in pharmaceutical development and manufacturing, especially in parenteral formulations and implantable drug delivery systems (IDDSs). Periprosthetic joint infections (PJIs) are a common complication in arthroplasties, with a prevalence of over 4%. There is still no treatment that fully covers the need for preventing and treating biofilm formation. However, 3D printing plays a major role in the development of novel therapies for PJIs. This review will provide a deep understanding of the different approaches based on 3D-printing techniques for the current management and prophylaxis of PJIs. The two main strategies are focused on IDDSs that are loaded or coated with antimicrobials, commonly in combination with bone regeneration agents and 3D-printed orthopedic implants with modified surfaces and antimicrobial properties. The wide variety of printing methods and materials have allowed for the manufacture of IDDSs that are perfectly adjusted to patients' physiognomy, with different drug release profiles, geometries, and inner and outer architectures, and are fully individualized, targeting specific pathogens. Although these novel treatments are demonstrating promising results, in vivo studies and clinical trials are required for their translation from the bench to the market.