The release kinetics, antimicrobial activity and cytocompatibility of differently prepared collagen/hydroxyapatite/vancomycin layers: Microstructure vs. nanostructure

Enhancing Guided Bone Regeneration with a Novel Carp Collagen Scaffold: Principles and Applications

Bone defects resulting from trauma, surgery, and congenital, infectious, or oncological diseases are a functional and aesthetic burden for patients. Bone regeneration is a demanding procedure, involving a spectrum of molecular processes and requiring the use of various scaffolds and substances, often yielding an unsatisfactory result. Recently, the new collagen sponge and its structural derivatives manufactured from European carp (Cyprinus carpio) were introduced and patented. Due to its fish origin, the novel scaffold poses no risk of allergic reactions or transfer of zoonoses and additionally shows superior biocompatibility, mechanical stability, adjustable degradation rate, and porosity. In this review, we focus on the basic principles of bone regeneration and describe the characteristics of an "ideal" bone scaffold focusing on guided bone regeneration. Moreover, we suggest several possible applications of this novel material in bone regeneration processes, thus opening new horizons for further research.

Preparation of multivesicular liposomes for the loco-regional delivery of Vancomycin hydrochloride using active loading method: drug release and antimicrobial properties

Over the last few years, among controlled-release delivery systems, multivesicular liposomes (MVLs) have attracted attention due to their unique benefits as a loco-regional drug delivery system. Considering the clinical limitations of the current treatment strategies for osteomyelitis, MVLs can be a suitable carrier for the local delivery of effective antibiotics. This study aimed to prepare vancomycin hydrochloride (VAN HL) loaded MVLs using the active loading method which to the best of our knowledge has not been previously reported. Empty MVLS were prepared by the double emulsion (w/o/w) method and VAN HL was loaded into the prepared liposomes by the ammonium gradient method. After full characterization, the release profile of VAN HL from MVLs was assessed at two different pH values (5.5 and 7.4), and compared with the release profile of the free drug and also passively loaded MVLs. In vitro antimicrobial activities were evaluated using the disc diffusion method. Our results demonstrated that the encapsulation efficiency was higher than 90% in the optimum actively loaded MVL. The free VAN HL was released within 6-8 h, while the passively loaded MVLs and the optimum actively loaded MVL formulation released the drug in 6 days and up to 19 days, respectively. The released drug showed effective antibacterial activity against osteomyelitis-causing pathogens. In conclusion, the prepared formulation offered the advantages of sustained-release properties, appropriate particle size as well as being composed of biocompatible materials, and thus could be a promising candidate for the loco-regional delivery of VAN HL and the management of osteomyelitis.

Functionalization of biomimetic mineralized collagen for bone tissue engineering

Mineralized collagen (MC) is the basic unit of bone structure and function and is the main component of the extracellular matrix (ECM) in bone tissue. In the biomimetic method, MC with different nanostructures of neo-bone have been constructed. Among these, extra-fibrous MC has been approved by regulatory agencies and applied in clinical practice to play an active role in bone defect repair. However, in the complex microenvironment of bone defects, such as in blood supply disorders and infections, MC is unable to effectively perform its pro-osteogenic activities and needs to be functionalized to include osteogenesis and the enhancement of angiogenesis, anti-infection, and immunomodulation. This article aimed to discuss the preparation and biological performance of MC with different nanostructures in detail, and summarize its functionalization strategy. Then we describe the recent advances in the osteo-inductive properties and multifunctional coordination of MC. Finally, the latest research progress of functionalized biomimetic MC, along with the development challenges and future trends, are discussed. This paper provides a theoretical basis and advanced design philosophy for bone tissue engineering in different bone microenvironments.

Recent Advances in Collagen Antimicrobial Biomaterials for Tissue Engineering Applications: A Review

Biomaterial-based therapies have been receiving attention for treating microbial infections mainly to overcome the increasing number of drug-resistant bacterial strains and off-target impacts of therapeutic agents by conventional strategies. A fibrous, non-soluble protein, collagen, is one of the most studied biopolymers for the development of antimicrobial biomaterials owing to its superior physicochemical, biomechanical, and biological properties. In this study, we reviewed the different approaches used to develop collagen-based antimicrobial devices, such as non-pharmacological, antibiotic, metal oxide, antimicrobial peptide, herbal extract-based, and combination approaches, with a particular focus on preclinical studies that have been published in the last decade.

Adipose-Derived Stem Cells in Reinforced Collagen Gel: A Comparison between Two Approaches to Differentiation towards Smooth Muscle Cells

Scaffolds made of degradable polymers, such as collagen, polyesters or polysaccharides, are promising matrices for fabrication of bioartificial vascular grafts or patches. In this study, collagen isolated from porcine skin was processed into a gel, reinforced with collagen particles and with incorporated adipose tissue-derived stem cells (ASCs). The cell-material constructs were then incubated in a DMEM medium with 2% of FS (DMEM_part), with added polyvinylalcohol nanofibers (PVA_part sample), and for ASCs differentiation towards smooth muscle cells (SMCs), the medium was supplemented either with human platelet lysate released from PVA nanofibers (PVA_PL_part) or with TGF-β1 + BMP-4 (TGF + BMP_part). The constructs were further endothelialised with human umbilical vein endothelial cells (ECs). The immunofluorescence staining of alpha-actin and calponin, and von Willebrand factor, was performed. The proteins involved in cell differentiation, the extracellular matrix (ECM) proteins, and ECM remodelling proteins were evaluated by mass spectrometry on day 12 of culture. Mechanical properties of the gels with ASCs were measured via an unconfined compression test on day 5. Gels evinced limited planar shrinkage, but it was higher in endothelialised TGF + BMP_part gel. Both PVA_PL_part samples and TGF + BMP_part samples supported ASC growth and differentiation towards SMCs, but only PVA_PL_part supported homogeneous endothelialisation. Young modulus of elasticity increased in all samples compared to day 0, and PVA_PL_part gel evinced a slightly higher ratio of elastic energy. The results suggest that PVA_PL_part collagen construct has the highest potential to remodel into a functional vascular wall.

Nanoantibiotics to fight multidrug resistant infections by Gram-positive bacteria: hope or reality?

The spread of antimicrobial resistance in Gram-positive pathogens represents a threat to human health. To counteract the current lack of novel antibiotics, alternative antibacterial treatments have been increasingly investigated. This review covers the last decade's developments in using nanoparticles as carriers for the two classes of frontline antibiotics active on multidrug-resistant Gram-positive pathogens, i.e., glycopeptide antibiotics and daptomycin. Most of the reviewed papers deal with vancomycin nanoformulations, being teicoplanin- and daptomycin-carrying nanosystems much less investigated. Special attention is addressed to nanoantibiotics used for contrasting biofilm-associated infections. The status of the art related to nanoantibiotic toxicity is critically reviewed.

An Additively Manufactured Sample Holder to Measure the Controlled Release of Vancomycin from Collagen Laminates

The controlled release of antibiotics prevents the spread of pathogens and thereby improves healing processes in regenerative medicine. However, high concentrations may interfere with healing processes. It is therefore advantageous to use biodegradable materials for a controlled release. In particular, multilayer materials enable differential release at different surfaces. For this purpose, collagen sheets of different properties can be bonded by photochemical crosslinking. Here, we present the development and application of an easily accessible, additively manufactured sample holder to study the controlled release of vancomycin from modularly assembled collagen laminates in two directions. As proof-of-concept, we show that laminates of collagen sheets covalently linked by rose bengal and green light crosslinking (RGX) can be tightly inserted into the device without leakage from the upper to lower cavity. We used this sample holder to detect the release of vancomycin from symmetrically and asymmetrically loaded two-layer and three-layer collagen laminates into the upper and lower cavity of the sample holder. We show that these collagen laminates are characterized by a collagen type-dependent vancomycin release, enabling the control of antibiotic release profiles as well as the direction of antibiotic release.

Antibacterial Poly(ε-CL)/Hydroxyapatite Electrospun Fibers Reinforced by Poly(ε-CL)-b-poly(ethylene phosphoric acid)

In bone surgery and orthopedics, bioresorbable materials can be helpful in bone repair and countering post-op infections. Explicit antibacterial activity, osteoinductive and osteoconductive effects are essential to achieving this objective. Nonwoven electrospun (ES) fibers are receiving the close attention of physicians as promising materials for wound dressing and tissue engineering; potentially, in high contrast with dense materials, ES mats hamper regeneration of the bone extracellular matrix to a lesser extent. The use of the compositions of inherently biodegradable polyesters (poly(ε-caprolactone) PCL, poly(lactoglycolide), etc.), calcium phosphates and antibiotics is highly prospective, but the task of forming ES fibers from such compositions is complicated by the incompatibility of the main organic and inorganic ingredients, polyesters and calcium phosphates. In the present research we report the synthesis of hydroxyapatite (HAp) nanoparticles with uniform morphology, and demonstrate high efficiency of the block copolymer of PCL and poly(ethylene phosphoric acid) (PEPA) as an efficient compatibilizer for PCL/HAp mixtures that are able to form ES fibers with improved mechanical characteristics. The materials obtained in the presence of vancomycin exhibited incremental drug release against Staphylococcus aureus (St. aureus).

Vancomycin-Loaded Collagen/Hydroxyapatite Layers Electrospun on 3D Printed Titanium Implants Prevent Bone Destruction Associated with S. epidermidis Infection and Enhance Osseointegration

The aim of the study was to develop an orthopedic implant coating in the form of vancomycin-loaded collagen/hydroxyapatite layers (COLHA+V) that combine the ability to prevent bone infection with the ability to promote enhanced osseointegration. The ability to prevent bone infection was investigated employing a rat model that simulated the clinically relevant implant-related introduction of bacterial contamination to the bone during a surgical procedure using a clinical isolate of Staphylococcus epidermidis. The ability to enhance osseointegration was investigated employing a model of a minipig with terminated growth. Six weeks following implantation, the infected rat femurs treated with the implants without vancomycin (COLHA+S. epidermidis) exhibited the obvious destruction of cortical bone as evinced via a cortical bone porosity of up to 20% greater than that of the infected rat femurs treated with the implants containing vancomycin (COLHA+V+S. epidermidis) (3%) and the non-infected rat femurs (COLHA+V) (2%). The alteration of the bone structure of the infected COLHA+S. epidermidis group was further demonstrated by a 3% decrease in the average Ca/P molar ratio of the bone mineral. Finally, the determination of the concentration of vancomycin released into the blood stream indicated a negligible systemic load. Six months following implantation in the pigs, the quantified ratio of new bone indicated an improvement in osseointegration, with a two-fold bone ingrowth on the COLHA (47%) and COLHA+V (52%) compared to the control implants without a COLHA layer (27%). Therefore, it can be concluded that COLHA+V layers are able to significantly prevent the destruction of bone structure related to bacterial infection with a minimal systemic load and, simultaneously, enhance the rate of osseointegration.

Review of the Applications of Biomedical Compositions Containing Hydroxyapatite and Collagen Modified by Bioactive Components

Regenerative medicine is becoming a rapidly evolving technique in today’s biomedical progress scenario. Scientists around the world suggest the use of naturally synthesized biomaterials to repair and heal damaged cells. Hydroxyapatite (HAp) has the potential to replace drugs in biomedical engineering and regenerative drugs. HAp is easily biodegradable, biocompatible, and correlated with macromolecules, which facilitates their incorporation into inorganic materials. This review article provides extensive knowledge on HAp and collagen-containing compositions modified with drugs, bioactive components, metals, and selected nanoparticles. Such compositions consisting of HAp and collagen modified with various additives are used in a variety of biomedical applications such as bone tissue engineering, vascular transplantation, cartilage, and other implantable biomedical devices.

Electrospun poly (vinyl alcohol) nanofibers incorporating caffeic acid/cyclodextrins through the supramolecular assembly for antibacterial activity

Here, we prepared the solid inclusion complexes between Caffeic acid (CA) and Cyclodextrins (β- and γ-CDs) (CA/CDs) that were effectively embedded into Poly (vinyl alcohol) (PVA) electrospun nanofibers via electrospinning technique to enhanced solubility and antibacterial activity. In tested Cyclodextrins are β-and γ-CDs with CA in the ratio of 1:1 resulting in the formation of CA/CDs by co-precipitation method. The physical properties of CA/CDs were examined by FT-IR, UV, and Raman Spectroscopy. The phase solubility test showed a much higher solubility of CA due to inclusion complexes (ICs). Furthermore, CA/β-CD and CA/γ-CD perfected achieved 0.70:1 and 0.80:1 the molar ratio of ICs, confirmed by NMR studies. The fiber size distribution, average diameter, and morphology features were evaluated by SEM analysis. The dissolution profile of PVA/CA and PVA/CA/CDs were tested within 150 min, resulting in CA dissolved in PVA/CA/CDs slightly higher than PVA/CA nanofibers due to enhanced solubility of ICs. Moreover, PVA/CA/CDs exhibit high antibacterial activity against gram-positive bacteria of E-Coli and gram-negative bacteria of S. aureus. Finally, these results suggest that PVA/CA/CDs may be promising materials for active food packaging applications.

The nuclear transporter importin-11 regulates the Wnt/β-catenin pathway and acts as a tumor promoter in glioma

Karyopherins mediate the macromolecular transport between the cytoplasm and the nucleus and participate in cancer progression. However, the role and mechanism of importin-11 (IPO11), a member of the karyopherin family, in glioma progression remain undefined. Effects of IPO11 on glioma progression were detected using CCK-8, colony formation assay, flow cytometry analysis, caspase-3 activity assay, and Transwell invasion assay. Western blot analysis was used to detect the expression of active caspase-3, active caspase-7, active caspase-9, N-cadherin, Vimentin, E-cadherin, β-catenin, and c-Myc. The activity of Wnt/β-catenin pathway was evaluated by the T-cell factor/lymphoid enhancer factor (TCF/LEF) transcription factor reporter assay. Results showed that IPO11 knockdown inhibited proliferation and reduced colony number in glioma cells. IPO11 silencing promoted the apoptotic rate, increased expression levels of active caspase-3, caspase-7, and caspase-9, and enhanced caspase-3 activity. Moreover, IPO11 silencing inhibited glioma cell invasion by suppressing epithelial-to-mesenchymal transition (EMT). Mechanistically, IPO11 knockdown inactivated the Wnt/β-catenin pathway. β-Catenin overexpression abolished the effects of IPO11 silencing on the proliferation, apoptosis, and invasion in glioma cells. Furthermore, IPO11 silencing blocked the malignant phenotypes and repressed the Wnt/β-catenin pathway in vivo. In conclusion, IPO11 knockdown suppressed the malignant phenotypes of glioma cells by inactivating the Wnt/β-catenin pathway.

Vancomycin-releasing cross-linked collagen sponges as wound dressings

The study presents a novel vancomycin-releasing collagen wound dressing derived from Cyprinus carpio collagen type I cross-linked with carbodiimide which retarded the degradation rate and increased the stability of the sponge. Following lyophilization, the dressings were subjected to gamma sterilization. The structure was evaluated via scanning electron microscopy images, micro-computed tomography, and infrared spectrometry. The structural stability and vancomycin release properties were evaluated in phosphate buffered saline. Microbiological testing and a rat model of a wound infected with methicillin-resistant Staphylococcus aureus (MRSA) were then employed to test the efficacy of the treatment of the infected wound. Following an initial mass loss due to the release of vancomycin, the sponges remained stable. After 7 days of exposure in phosphate buffered saline (37°C), 60% of the material remained with a preserved collagen secondary structure together with a high degree of open porosity (over 80%). The analysis of the release of vancomycin revealed homogeneous distribution of the antibiotic both across and between the sponges. The release of vancomycin was retarded as proved by in vitro testing and further confirmed by the animal model from which measurable concentrations were observed in blood samples 24 hours after the subcutaneous implantation of the sponge, which was more than observed following intraperitoneal administration. The sponge was also highly effective in terms of reducing the number of colony-forming units in biopsies extracted from the infected wounds 4 days following the inoculation of the wounds with the MRSA solution. The presented sponges have ideal properties to serve as wound dressing for prevention of surgical site infection or treatment of already infected wounds.

Hydrothermal synthesis of perfectly shaped micro- and nanosized carbonated apatite

Herein we present a Ca[EDTA]-based synthesis and comparative study of perfectly shaped plate-like, rod–like, and prism-like carbonated apatites.

Shapable bulk agarose-gelatine-hydroxyapatite-minocycline nanocomposite fabricated using a mineralising system aided with electrophoresis for bone tissue regeneration

To develop a shapable bulk antibacterial nanocomposite biomaterial for bone regeneration. A bulk agarose-gelatine hydrogel was through mineralised using a hydrogel mineralising system aided with electrophoresis, and the mineralised hydrogel was loaded with minocycline to obtain the agarose-gelatine-hydroxyapatite-minocycline nanocomposite. The nanocomposite had a large BET surface area of 44.4518m2/g and a high porosity of 76.9%. Hydroxyapatite crystals were well developed in the hydrogel matrix and exhibited a hybrid structure of microscale and nanoscale motifs. The addition of minocycline resulted in a continuous antibiotic release, inhibiting the growth of Staphylococcus aureus over two weeks in vitro. Exposed to rabbit bone marrow mesenchymal stem cells, the nanocomposite revealed good cytocompatibility in vitro. Furthermore, the biomaterial could effectively enhance the bone regeneration in a critical-size rabbit cranial defect model in vivo. These findings depicted that the nanocomposite, with good biocompatibility and good antibacterial property, is a promising candidate for future clinical application in bone tissue engineering or as a prospective bone replacement biomaterial.

Rifampin-Releasing Triple-Layer Cross-Linked Fresh Water Fish Collagen Sponges as Wound Dressings

Objectives

Surgical wounds resulting from biofilm-producing microorganisms represent a major healthcare problem that requires new and innovative treatment methods. Rifampin is one of a small number of antibiotics that is able to penetrate such biofilms, and its local administration has the potential to serve as an ideal surgical site infection protection and/or treatment agent. This paper presents two types (homogeneous and sandwich structured) of rifampin-releasing carbodiimide-cross-linked fresh water fish collagen wound dressings.

Methods

The dressings were prepared by means of the double-lyophilization method and sterilized via gamma irradiation so as to allow for testing in a form that is able to serve for direct clinical use. The mechanical properties were studied via the uniaxial tensile testing method. The in vivo rifampin-release properties were tested by means of a series of incubations in phosphate-buffered saline. The microbiological activity was tested against methicillin-resistant staphylococcus aureus (MRSA) employing disc diffusion tests, and the in vivo pharmacokinetics was tested using a rat model. A histological examination was conducted for the study of the biocompatibility of the dressings.

Results

The sandwich-structured dressing demonstrated better mechanical properties due to its exhibiting ability to bear a higher load than the homogeneous sponges, a property that was further improved via the addition of rifampin. The sponges retarded the release of rifampin in vitro, which translated into at least 22 hours of rifampin release in the rat model. This was significantly longer than was achieved via the administration of a subcutaneous rifampin solution. Microbiological activity was proven by the results of the disc diffusion tests. Both sponges exhibited excellent biocompatibility as the cells penetrated into the scaffold, and virtually no signs of local irritation were observed.

Conclusions

We present a novel rifampin-releasing sandwich-structured fresh water fish collagen wound dressing that has the potential to serve as an ideal surgical site infection protection and/or treatment agent.

N-(9-Fluorenylmethoxycarbonyl)-L-Phenylalanine/nano-hydroxyapatite hybrid supramolecular hydrogels as drug delivery vehicles with antibacterial property and cytocompatibility

The intrinsic fragility of hydroxyapatite (HAP) restricts its wider applications for local delivery of antibiotics. The composites formed by integrating HAP with hydrogels can improve the properties of HAP. However, these reported composites not only require tedious preparation and employ organic solvent and toxic reagents, but also hardly have inherent antimicrobial property. In this study, N-(9-Fluorenylmethoxycarbonyl)-L-Phenylalanine/nano-hydroxyapatite (Fmoc-L-Phe/nHAP) hybrid supramolecular hydrogels with antibacterial property and cytocompatibility was prepared by integrating nHAP as reinforcement with Fmoc-L-Phe supramolecular hydrogels. The results showed that nHAP bounds in the chamber of the gel network and adheres to the fiber of Fmoc-L-Phe due to intermolecular interaction, remarkably improving the mechanical strength of Fmoc-L-Phe supramolecular hydrogels. The results of inhibition zone experiment and MTT experiment showed that the Fmoc-L-Phe/nHAP hybrid supramolecular hydrogels possess antimicrobial property and cytocompatibility. In vitro release experiment of chlorogenic acid (CGA) from the hybrid supramolecular hydrogels was performed. The study of the release kinetics indicated that the release behavior of CGA from the hybrid supramolecular hydrogels is following Weibull model and release mechanism involved Fickian diffusion and erosion of the surface of hydrogel matrix. The release of CGA shows a good inhibition effect on S. aureus. The results show that the Fmoc-L-Phe/nHAP hybrid hydrogels with antibacterial property and cytocompatibility have promising applications as drug delivery carrier. Due to the intrinsic fragility of hydroxyapatite (HAP), the properties of HAP could be improved by incorporation into hydrogels. However, these reported composites not only require tedious preparation and employ organic solvent and toxic reagents, but also hardly have inherent antimicrobial property. We prepared N-(9-Fluorenylmethoxycarbonyl)-L-Phenylalanine/nano-hydroxyapatite (Fmoc-L-Phe/nHAP) hybrid supramolecular hydrogels by integrating nHAP as reinforcement with Fmoc-L-Phe supramolecular hydrogels. The results showed that nHAP bounds in the chamber of the gel network and adheres to the fiber of Fmoc-L-Phe due to intermolecular interaction, remarkably improving the mechanical strength of Fmoc-L-Phe supramolecular hydrogels. The results of inhibition zone experiment and MTT experiment showed that the Fmoc-L-Phe/nHAP hybrid supramolecular hydrogels possess antibacterial property and cytocompatibility. In vitro release experiment of chlorogenic acid (CGA) from the hybrid supramolecular hydrogels was performed. The study of the release kinetics indicated that the release behavior of CGA from the hybrid supramolecular hydrogels is following Weibull model and release mechanism involved Fickian diffusion and erosion of the surface of hydrogel matrix. The release of CGA shows a good inhibition effect on S. aureus. The results show that the Fmoc-L-Phe/nHAP hybrid hydrogels with antibacterial property and cytocompatibility have promising applications as drug delivery carrier.

Surface Treatment of Acetabular Cups with a Direct Deposition of a Composite Nanostructured Layer Using a High Electrostatic Field

A composite nanofibrous layer containing collagen and hydroxyapatite was deposited on selected surface areas of titanium acetabular cups. The layer was deposited on the irregular surface of these 3D objects using a specially developed electrospinning system designed to ensure the stability of the spinning process and to produce a layer approximately 100 micrometers thick with an adequate thickness uniformity. It was verified that the layer had the intended nanostructured morphology throughout its entire thickness and that the prepared layer sufficiently adhered to the smooth surface of the model titanium implants even after all the post-deposition sterilization and stabilization treatments were performed. The resulting layers had an average thickness of (110 ± 30) micrometers and an average fiber diameter of (170 ± 49) nanometers. They were produced using a relatively simple and cost-effective technology and yet they were verifiably biocompatible and structurally stable. Collagen- and hydroxyapatite-based composite nanostructured surface modifications represent promising surface treatment options for metal implants.

The Significance and Utilisation of Biomimetic and Bioinspired Strategies in the Field of Biomedical Material Engineering: The Case of Calcium Phosphat-Protein Template Constructs

This review provides a summary of recent research on biomimetic and bioinspired strategies applied in the field of biomedical material engineering and focusing particularly on calcium phosphate-protein template constructs inspired by biomineralisation. A description of and discussion on the biomineralisation process is followed by a general summary of the application of the biomimetic and bioinspired strategies in the fields of biomedical material engineering and regenerative medicine. Particular attention is devoted to the description of individual peptides and proteins that serve as templates for the biomimetic mineralisation of calcium phosphate. Moreover, the review also presents a description of smart devices including delivery systems and constructs with specific functions. The paper concludes with a summary of and discussion on potential future developments in this field.

Microspheres of alginate encapsulated minocycline-loaded nanocrystalline carbonated hydroxyapatite: therapeutic potential and effects on bone regeneration

Background and objective: Tetracycline and its derivatives, combined with calcium phosphates, have been proposed as a delivery system to control inflammatory processes and chronic infections. The objective of this study was to evaluate the microspheres of alginate encapsulated minocycline-loaded nanocrystalline carbonated hydroxyapatite (CHAMINO) as a biomimetic device to carry out target-controlled drug delivery for alveolar bone repair.

Methods: CHAMINO microspheres were implanted in a rat central incisor socket after 7 and 42 days. New bone was formed in both groups between 7 and 42 days of implantation. However, the bone growth was significantly higher for the CHAMINO microspheres.

Results: The minocycline (MINO) loading capacity of the nanocrystaline carbonated hydroxyapatite (CHA) nanoparticles was 25.1±2.2 µg MINO/mg CHA for adsorption over 24 hrs. The alginate microspheres containing minocycline-loaded CHA were biologically active and inhibited the Enterococcus faecalis culture growth for up to seven days of the MINO release. An osteoblastic cell viability assay based on the resazurin reduction was conducted after the cells were exposed to the CHAMINO powder and CHAMINO microspheres. Thus, it was found that the alginate extracts encapsulated the minocycline-loaded CHA microspheres and did not affect the osteoblastic cell viability, while the minocycline-doped CHA powder reduced the cell viability by 90%.

Conclusion: This study concluded that the alginate microspheres encapsulating the minocycline-loaded nanocrystalline carbonated hydroxyapatite exhibited combined antibacterial activity against Enterococcus faecalis with cytocompatibility and osteoconduction properties. The significant improvement in the new bone formation after 42 days of implantation suggests that the CHAMINO microsphere has potential in clinical applications of bone regeneration.

Evaluation of collagen/hydroxyapatite electrospun layers loaded with vancomycin, gentamicin and their combination: Comparison of release kinetics, antimicrobial activity and cytocompatibility

The aim of this study was to develop a biodegradable nanostructured electrospun layer based on collagen (COL), hydroxyapatite nanoparticles (HA), vancomycin hydrochloride (V), gentamicin sulphate (G) and their combination (VG) for the treatment of prosthetic joint infections and the prevention of infection during the joint replacement procedure. COL/HA layers containing different amounts of HA (0, 5 and 15 wt%) were tested for the in vitro release kinetics of antibiotics, antimicrobial activity against MRSA, gentamicin-resistant Staphylococcus epidermidis and Enterococcus faecalis isolates and cytocompatibility using SAOS-2 bone-like cells. The results revealed that the COL/HA layers released high concentrations of vancomycin and gentamicin for 21 days and performed effectively against the tested clinically-relevant bacterial isolates. The presence of HA in the collagen layers was found not to affect the release kinetics of the vancomycin from the layers loaded only with vancomycin or its combination with gentamicin. Conversely, the presence of HA slowed down the release of gentamicin from the COL/HA layers loaded with gentamicin and its combination with vancomycin. The combination of both antibiotics exerted a positive effect on the prolongation of the conversion of vancomycin into its degradation products. All the layers tested with different antibiotics exhibited potential antibacterial activity with respect to both the tested staphylococci isolates and enterococci. The complemental effect of vancomycin was determined against both gentamicin-resistant Staphylococcus epidermidis and Enterococcus faecalis in contrast to the application of gentamicin as a single agent. This combination was also found to be more effective against MRSA than is vancomycin as a single agent. Importantly, this combination of vancomycin and gentamicin in the COL/HA layers exhibited sufficient cytocompatibility to SAOS-2, which was independent of the HA content. Conversely, only gentamicin caused the death of SAOS-2 independently of HA content and only vancomycin stimulated SAOS-2 behaviour with an increased concentration of HA in the COL/HA layers. In conclusion, COL/HA layers with 15 wt% of HA impregnated with vancomycin or with a combination of vancomycin and gentamicin offer a promising treatment approach and the potential to prevent infection during the joint replacement procedures.

A novel gentamicin-releasing wound dressing prepared from freshwater fish Cyprinus carpio collagen cross-linked with carbodiimide

Our study presents a novel collagen wound dressing prepared from freshwater fish skin ( Cyprinus Carpio) collagen type I. Half of the sponges were cross-linked with carbodiimide. The cross-linked and non-cross-linked collagen sponges were subsequently impregnated with gentamicin and lyophilized thus allowing for the attainment of the appropriate gentamicin content without the removal thereof during the cross-linking stage. The structure was evaluated via micro-CT and infrared spectrometry and the structural stability and gentamicin release properties were evaluated in phosphate buffer solution. The sponges were further tested via a rat model of an infected wound with Pseudomonas aeruginosa inoculation and compared with a reference commercial product. The sponges thus prepared provided a degree of open porosity that was comparable to or higher than that of the reference commercial product. Spectrometry analysis revealed that the cross-linked collagen sponge and reference commercial product sponge preserved their secondary collagen structure after 168 h while early accelerated degradation was observed with respect to the non-cross-linked collagen sponge. Gentamicin was released rapidly from all the sponges. Compared to those animals with gentamicin-containing sponges or gentamicin administered intramuscularly, the animals with the cross-linked collagen sponge without gentamicin exhibited marked clinical and laboratory infection signs. Both the administration routes (intramuscular and via gentamicin-containing sponges) provided similar gentamicin plasma levels. The resulting highly homogeneous product which was characterized by excellent structural and clinical properties proved effective in terms of the treatment of a surgical wound infection in a rat model. We demonstrated that all the gentamicin was released from the sponge and was absorbed in the systemic circulation. This is the first time that Cyprinus Carpio collagen has been used in the preparation of wound dressings. Thus, gentamicin-containing sponges provide a promising tool for the treatment and prevention of surgical site infections.