In vitro release of gentamicin from OHAp/PEMA/PMMA samples

Release of vancomycin and tobramycin from polymethylmethacrylate cements impregnated with calcium polyphosphate hydrogel

The influence of calcium polyphosphate (CPP) gel incorporation on the release of vancomycin and tobramycin from polymethyl methacrylate (PMMA) cement (Simplex P, SP) has been studied. Adding 10% CPP gel to SP led to a much lower burst release of vancomycin and considerably extended release of both vancomycin and tobramycin up to 24 weeks. Antibiotics released from this new material retain their bactericidal activity for up to 15 weeks. The improvement in the antibiotic release is mainly due to the molecular interactions of antibiotics with embedded CPP polyphosphate chains as confirmed by Raman spectroscopy analysis. The inclusion of CPP hydrogel also increased the SP surface roughness and pore sizes, leading to a higher release rate of antibiotics. The new material is biocompatible and has similar handling properties and mechanical strength as compared to SP cements. We believe that incorporating CPP gel provides a better and usable drug carrier for PMMA cement. © 2017 The Authors Journal of Biomedical Materials Research Part B: Applied Biomaterials Published by Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 2827-2840, 2018.

Antibiotic-eluting hydrophilized PMMA bone cement with prolonged bactericidal effect for the treatment of osteomyelitis

Osteomyelitis is still considered to be one of the major challenges for orthopedic surgeons despite advanced antiseptic surgical procedures and pharmaceutical therapeutics. In this study, hydrophilized poly(methyl methacrylate) (PMMA) bone cements containing Pluronic F68 (EG79PG28EG79) as a hydrophilic additive and vancomycin ( F68-VA cements) were prepared to allow the sustained release of the antibiotic for adequate periods of time without any significant loss of mechanical properties. The compressive strengths of the bone cements with Pluronic F68 compositions less than 7 wt% were not significantly different compared with the control vancomycin-loaded bone cement ( VA cement). The F68 (7 wt%)-VA cement showed sustained release of the antibiotic for up to 11 weeks and almost 100% release from the bone cement. It also prohibited the growth of S. aureus (zone of inhibition) over six weeks (the required period to treat osteomyelitis), and it did not show any notable cytotoxicity. From an animal study using a femoral osteomyelitis rat model, it was observed that the F68 (7 wt%)-VA cement was effective for the treatment of osteomyelitis, probably as a result of the prolonged release of antibiotic from the PMMA bone cement. On the basis of these findings, it can be suggested that the use of Pluronic F68 as a hydrophilic additive for antibiotic-eluting PMMA bone cement can be a promising strategy for the treatment of osteomyelitis.

Evaluation of Elution and Mechanical Properties of High-Dose Antibiotic-Loaded Bone Cement: Comparative "In Vitro" Study of the Influence of Vancomycin and Cefazolin

Use of antibiotic-loaded bone cements is one of the most effective methods for the prevention and treatment of prosthetic joint infection. However, there is still controversy about the optimal combination and doses of antibiotics that provide the maximum antimicrobial effect without compromising cement properties. In this study, vancomycin and cefazolin were added to a bone cement (Palacos R+G). Antibiotic release, fluid absorption, and mechanical properties were evaluated under physiological conditions. The results show that the type of antibiotic selected has an important impact on cement properties. In this study, groups with cefazolin showed much higher elution than those containing the same concentration of vancomycin. In contrast, groups with cefazolin showed a lower strength than vancomycin groups.

Antibiotic loading on bioactive glasses and glass-ceramics: An approach to surface modification

A bioactive glass and its corresponding glass-ceramic have been used to investigate the possibility to load a common antibiotic (carbenicillin) on their surface during the reactivity processes which occur by dipping these materials in a simulated body fluid. The materials bioactivity in the early stage of simulated body fluid treatment has been investigated by means of scanning electron microscopy (SEM-EDS) and X-ray diffraction. The uptake of carbenicillin has been performed by dipping the samples in simulated body fluid solution with a drug concentration of 500 mg/l for 6, 12 and 24 h. Some glass samples underwent a pre-treatment in simulated body fluid, for different time frames, in order to form a silica gel layer before the surface exposition to antibiotic. The carbenicillin release has been measured in water up to 36 h. The amount of incorporated and released antibiotic has been estimated by UV visible spectrophotometer. All samples were able to incorporate a significant amount of antibiotic and it was possible to tailor the drug release by modifying the simulated body fluid pre-treatment.

Mesoporous silica nanoparticle-functionalized poly(methyl methacrylate)-based bone cement for effective antibiotics delivery

Poly(methyl methacrylate)-based bone cements are functionalized with mesoporous silica nanoparticles (MSN) to enable a highly efficient and sustained release of antibiotics to reduce the risk of post-operative joint infection. To overcome the limited drug release of 5% for only 1 day with the current commercial-grade bone cements, a 8 wt% MSN-formulated bone cement is able to increase the drug release efficiency by 14-fold and sustain the release for up to 80 days. The loaded MSN is suggested to build up an effective network of rod-shaped silica particles with uniformly arranged nanoporous channels, which is responsible for the effective drug diffusion and extend time-release to the external surfaces. MSN has no detrimental effect on the critical weight-bearing bending modulus and compression strength of bone cement. In vitro assay test results show a much sustained antibacterial effect and low cytotoxicity of MSN demonstrating the potential applicability of MSN-formulated bone cement.

Organic-inorganic composites for bone drug delivery

This review paper attempts to provide an overview in the fabrication and application of organic-inorganic based composites in the field of local drug delivery for bone. The concept of local drug delivery exists for a few decades. However, local drug delivery in bone and specially application of composites for delivery of drugs to bone is an area for potential research interest in the recent time. The advantages attained by an organic-inorganic composite when compared to its individual components include their ability to release drug, adopting to the natural environment and supporting local area until complete bone regeneration, which make them carriers of interest for local drug delivery for bone.

SBA-15 ordered mesoporous silica inside a bioactive glass-ceramic scaffold for local drug delivery

The paper reports the synthesis of an ordered silica mesostructure of the SBA-15 type inside a macroporous bioactive glass-ceramic scaffold of the type SiO(2)-CaO-K(2)O, to combine the bioactivity of the latter with the release properties of the former, in view of local drug delivery from implants designed for tissue engineering. The standard procedure for SBA-15 synthesis has been modified to minimize the damage to the scaffold caused by the acidic synthesis medium. The composite system has been characterized by means of Scanning Electron Microscopy (coupled with EDS analysis), Small Angle X-Ray Diffraction, Thermogravimetry analysis and Infrared Spectroscopy: the formation of a well ordered hexagonal mesostructure was confirmed. Ibuprofen has been chosen as model drug. The uploading properties have been investigated of the scaffold-mesoporous silica composite as compared with the scaffold as such, and a five-fold increase in the adsorbing properties toward ibuprofen was found, due to the presence of the ordered mesoporous silica. The ibuprofen release to a SBF solution in vitro is complete in 1 day. Retention of bioactivity from the glass-ceramic scaffold after the silica mesostructure incorporation has been observed.

Ordered Mesoporous Materials in the Context of Drug Delivery Systems and Bone Tissue Engineering

Chemistry, materials science and medicine are research areas that converge in the field of drug delivery systems and tissue engineering. This paper tries to introduce an example of such an interaction, aimed at solving health issues within the world of biomaterials. Ordered mesoporous materials can be loaded with different organic molecules that would be released afterwards, in a controlled fashion, inside a living body. These materials can also react with the body fluids giving rise to carbonated nanoapatite particles as the products of such a chemical interaction; these particles, equivalent to biological apatites, enable the regeneration of bone tissue.

Chlorhexidine-releasing methacrylate dental composite materials

Light curable antibacterial, dental composite restoration materials, consisting of 80 wt% of a strontium fluoroaluminosilicate glass dispersed in methacrylate monomers have been produced. The monomers contained 40-100 wt% of a 10 wt% chlorhexidine diacetate (CHXA) in hydroxyethylmethacrylate (HEMA) solution and 60-0 wt% of a 50/50 mix of urethane dimethacrylate (UDMA) and triethyleneglycol dimethacrylate (TEGDMA). On raising HEMA content, light cure polymerisation rates decreased. Conversely, water sorption induced swelling and rates of diffusion controlled CHXA release from the set materials increased. Experimental composites with 50 and 90 wt% of the CHXA in HEMA solution in the monomer were shown, within a constant depth film fermentor (CDFF), to have slower rates of biofilm growth on their surfaces between 1 and 7 days than the commercial dental composite Z250 or fluoride-releasing dental cements, Fuji II LC and Fuji IX. When an excavated bovine dentine cylinder re-filled with Z250 was placed for 10 weeks in the CDFF, both bacteria and polymers from the artificial saliva penetrated between the material and dentine. With the 50 wt% experimental HEMA/CHXA formulation, this bacterial microleakage was substantially reduced. Polymer leakage, however, still occurred. Both polymer and bacterial microleakage were prevented with a 90 wt% HEMA/CHXA restoration in the bovine dentine due to swelling compensation for polymerisation shrinkage in combination with antibacterial release.

Incorporation of different antibiotics into carbonated hydroxyapatite coatings on titanium implants, release and antibiotic efficacy

Carbonated hydroxyapatite (CHA) coatings were applied onto titanium implants by using a biomimetic precipitation method. Different antibiotics were incorporated into the CHA coatings and their release and efficacy against bacteria growth were studied in vitro. The following antibiotics were used within this study: cephalothin, carbenicillin, amoxicillin, cefamandol, tobramycin, gentamicin and vancomycin. Increased concentrations of antibiotics in the coating solution led to a higher quantity of antibiotic incorporated into the CHA coating. Some antibiotics were better incorporated than others depending on their chemical structure. Antibiotics, containing carboxylic groups such as cephalothin, carbenicillin and cefamandol, were better incorporated than antibiotics lacking these groups. A bacterial inhibition test on Staphylococcus aureus bacteria showed inhibition of growth for all antibiotics that were released from the CHA coating. A release test was conducted in phosphate buffer saline PBS at pH 7.4 and 37 degrees C and showed that antibiotics containing carboxylic groups like cephalothin were slower released from the CHA coating than others. These results suggest that certain antibiotics are able to bind/chelate with calcium, resulting in a better incorporation into the CHA coating and a slower release. Antibiotics incorporated in CHA coatings on titanium implants might be used to prevent post-surgical infections and to promote bone-bonding of orthopedic devices.

Gentamicin-loaded calcium carbonate materials: Comparison of two drug-loading modes

Synthetic aragonite-based porous materials were drug loaded with gentamicin sulphate, an antibiotic active on Staphylococcus aureus responsible for osteomyelitis. Drug loading was accomplished by two different ways: by integration of gentamicin in material during processing or by soaking material into gentamicin solutions. We first investigated the influence of drug loading on compressive strength of materials. Results indicate that soaked materials presented the same compressive strength than unloaded materials with the same porosity. By contrast, the integration of gentamicin during processing increased significantly the compressive strength of materials. The materials drug content before elution was a least 10 times higher when gentamicin was integrated during processing comparatively to soaked materials. The study of in vitro gentamicin release showed that for materials with gentamicin integrated during material processing, high concentrations of gentamicin were released up to 8 or 12 days, against 4 days for soaked materials. The transport coefficients calculation, for the first step of release, indicated that the rate of release was higher for materials with integrated gentamicin because of the higher gentamicin content. The porosity rate influenced the rate of release for materials positively with gentamicin integrated during processing contrary to soaked materials for which a higher porosity rate allowed a deeper penetration of gentamicin during drug loading and then a slightly slower release. Results indicate that aragonite-based material with gentamicin integrated during material processing may be used either as resorbable device for release of high concentrations of gentamicin or as biomaterial for combined therapy: bone substitution and prevention or treatment of osteomyelitis.

In vitro Measurement of the Time-Related Efficacy of Gentamicin Sulfate Release from Bone Cements

BACKGROUND

The aim of the present study was to establish an in vitro microbiologic monitoring system which measures the dynamics of antibiotic release from acrylic bone cement and its antibacterial efficacy.

METHODS

Palacos R and Orthofix R cements containing gentamicin sulfate were tested. The in vitro elution dynamics was analyzed by plate diffusion method during a 1-year period after mixing. High but rapidly decreasing antibiotic levels were detected within the 1st week, resulting in an almost steadily low concentration by the end of the 1st month. After 1 year, it was still possible to demonstrate the inhibitory effect of the drug from both cements. Comparison of the time-related release between the antibiotics failed to find any statistically significant differences.

CONCLUSION

The method described is a useful and reproducible technique for the in vitro measurement of the inhibitory activity of antibiotic released from bone cements.

Effect of lactide/glycolide monomers on release behaviors of gentamicin sulfate-loaded PLGA discs

In order to develop the desirable drug release patterns such as no lag time and exact zero-order release rate, gentamicin sulfate (GS)-loaded poly(D,L-lactide-co-glycolide) (PLGA) discs containing lactide monomer (LM) or glycolide monomer (GM) were prepared. LM or GM was applied for the controlling drug release pattern due to its non-toxic and biodegradable nature. Water absorption, mass loss, pH change, and morphology of discs were examined to study the effect of LM or GM addition. GS release showed near zero-order profile in the GS-loaded polymeric discs prepared in the presence of LM or GM (10%). The channel of GS-loaded PLGA containing LM or GM was formed by the dissolution of LM or GM. Water uptake of disc increased till 21 days from the beginning of the test. The pH variations of media declined in the same manner with the result of mass loss. The antibiosis of GS was also confirmed by bacterial inhibition zone test using the prepared polymeric discs. From these results, we expected that the polymeric discs containing LM or GM would be a good dosage form as a topically implantable device which can get rid of lag period from PLGA matrix.

Mesoporous SBA-15 HPLC evaluation for controlled gentamicin drug delivery

Mesoporous silica SBA-15 was prepared to evaluate its application as gentamicin drug delivery system. Two procedures were used to evaluate the delivery: calcined powder and disk conformed. The samples were charged with gentamicin sulphate and the experiments were carried out in vitro. No significant difference between powder and disk was observed in the tests. The release profiles exhibited a pronounced initial burst release effect of 60%, followed by a very slow release pattern. A new HPLC method was employed for calculated gentamicin amount in the delivery test. This method requires a small amount of sample, very advisable in these kinds of assays.

Development of hydroxyapatite bone scaffold for controlled drug release via poly(?-caprolactone) and hydroxyapatite hybrid coatings

A scaffold-coating design, the hydroxyapatite (HA) porous bone scaffold coated with poly(epsilon-)caprolactone (PCL) and HA powder hybrids, was developed for use as tissue-regeneration and controlled-release system. An antibiotic drug, tetracycline hydrochloride (TCH), was encapsulated within the hybrid coating layer through a dip-coating and solvent-casting method. Coating cycle and drug loading amount differed to control the level of drug-release rate. The HA scaffold framework, obtained by a polymeric foam reticulate method, exhibited a highly porous structure, with porosity and pore size of approximately 87% and 180 microm, respectively. The hybrid layer, consisting of PCL sheet and HA fine powders, was uniformly coated on the scaffold surface. The coating layer exhibited only PCL and HA phases and structures, revealing no chemical interaction among the coating components, as observed by X-ray diffraction (XRD) and Fourier-transform infrared (FTIR) analyses. The coated-HA scaffolds showed an effective stress distribution behavior in response to an applied load, as confirmed by the compressive stress-strain curve. The mechanical properties of the coated scaffolds were improved highly with coatings; the compressive strength and elastic modulus of the cyclic coated scaffolds were approximately 3-4 times, and the energy absorption were approximately 8 times, higher than those without coating. These improvements were attributed mainly to the shielding of framework flaws by a flexible coating layer and partially to the thicker stems (porosity reduction). The dissolution of the coated scaffolds in a phosphate-buffered saline (PBS) solution increased with incubation time. The drug was released sharply within the initial several hours ( approximately 2 h), but the rate decreased further, showing a sustained release. The release amount was well controlled via coating-cycle and initial drug loading amount, suggesting the effectiveness of the coating-scaffold design as a drug-delivery system.