Zinc-doped hydroxyapatite as a pH responsive drug delivery system for anticancer drug 6-mercaptopurine.

6-Mercaptopurine (6MP) is commonly used in the treatment of acute lymphoblastic leukemia as an important agent in maintenance therapy. Despite its therapeutic benefits, 6MP has some limitations during therapy. Taking into account the disadvantages during 6MP therapy, there is a great need to create an appropriate delivery system for this drug. 6MP contains in its structure nitrogen and sulfur atoms capable of forming coordination compounds with metal ions, for example zinc. Therefore, in this work, we prepared biocompatible hydroxyapatite (HAp) doped with zinc ions, and used it as a carrier for 6MP. Doped HAp has not been used as a carrier for this drug before. The work proved that the prepared carrier-drug system has a particle size of about 130 nm, which indicates its potential for intravenous delivery. In addition, in an acidic environment (imitating cancer cells), the carrier agglomerates allow targeted release of the drug. The drug is evenly distributed, which indicates that the doses released from it will always be comparable. The release of the drug in a neutral environment is long-lasting in controlled doses, whereas in an acidic environment it is immediate. The obtained results indicate the high potential of the material in both slow-release and cancer-targeted release of 6MP.

Double Hydroxyl Salt as Smart Biocompatible pH-Responsive Carrier for 6-Mercaptopurine.

Hydroxy double salts are layered materials that are considered to be biocompatible. For this reason, research has been initiated on the possibility of their use in drug delivery. Despite their use for several types of drugs, their potential for controlled release of mercaptopurine (MERC) has not been studied. In this work, the synthesized hydroxy double salt (HDS) material was used as a carrier for this drug for the first time. The effectiveness of HDS synthesis has been proven by such techniques as X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM). Based on the FT-IR and energy-dispersive X-ray spectroscopy (EDS) results, the effectiveness of drug sorption was proven. The exact amount of drug retained was determined by the UV-Vis technique. The obtained results indicate that the drug is evenly distributed on the surface of the carrier, which is important during the controlled delivery of drugs. In the most important stage of the research, the effectiveness of drug release in response to changes in the pH of the environment was proven. The drug is not released into an environment that mimics healthy human tissues. It is released only after contact with the acidic environment that usually surrounds cancer cells. The low cellular toxicity of HDS and significant cytotoxic effect of HDS-MERC were confirmed by in vitro studies on MCF-7 human breast and DU145 prostate cancer cell lines and non-cancerous keratinocytes HaCaT. Interestingly, coupling with the HDS carrier increased the cytotoxic effect of MERC towards DU145 cells. Such an "intelligent" drug carrier for mercaptopurine has not been previously described in the literature. The obtained results indicate its great potential.

Zeolites with Divalent Ions as Carriers in the Delivery of Epigallocatechin Gallate.

Epigallocatechin gallate (EGCG) is a compound with very high therapeutic potential in the treatment of osteoporosis and cancer. The disadvantages of this compound are its low stability and low bioavailability. Therefore, carriers for EGCG are sought to increase its use. In this work, new carriers are proposed, i.e., zeolites containing divalent ions of magnesium, calcium, strontium, and zinc in their structure. EGCG is retained on the carrier surface by strong interactions with divalent ions. Due to the presence of strong interactions, EGCG is released in a controlled manner from the carrier-ion-EGCG drug delivery system. The results obtained in this work confirm the effectiveness of the preparation of new carriers. EGCG is released from the carriers depending on the pH; hence, it can be used both in osteoporosis and in the treatment of cancer. The divalent ion used affects the sorption and release of the drug. The obtained results indicate the great potential of the proposed carriers and their advantage over the carriers described in the literature.

Surface Modification of Ti6Al4V ELI Titanium Alloy by Poly(ethylene-alt-maleic anhydride) and Risedronate Sodium.

With the simultaneous increase in the number of endoprostheses being performed, advances in the field of biomaterials are becoming apparent-whereby the materials and technologies used to construct implants clearly improve the implants' quality and, ultimately, the life of the patient after surgery. The aim of this study was to modify the titanium alloy Ti6Al4V ELI used in the construction of hip joint endoprostheses. This is why the continuous development of biomaterials is so important. This paper presents the results of research for a new application of polymer poly(ethylene-alt-maleic anhydride) as a drug release layer, placed on the surface of a titanium alloy. The obtained layers were analyzed using Raman spectroscopy (spectra and maps), Fourier transform infrared spectroscopy (spectra and maps), contact angle measurements as well as scanning electron microscopy and energy dispersive spectroscopy imaging and topography analysis. The results confirmed that the polymer layer obtained on the plate surface after the alkali heat treatment process is much better-it binds much more polymer and thus the applied drug. In addition, a longer and more gradual release of the drug was observed for the alkali heat treatment modification than for H2O2 solution.

Mesoporous Silica Modified with Polydopamine and Zinc Ions as a Potential Carrier in the Controlled Release of Mercaptopurine.

Mercaptopurine is one of the drugs used in the treatment of acute lymphoblastic leukemia. A problem with mercaptopurine therapy is its low bioavailability. This problem can be solved by preparing the carrier that releases the drug in lower doses but over a longer period of time. In this work, polydopamine-modified mesoporous silica with adsorbed zinc ions was used as a drug carrier. SEM images confirm the synthesis of spherical carrier particles. The particle size is close to 200 nm, allowing for its use in intravenous delivery. The zeta potential values for the drug carrier indicate that it is not prone to agglomeration. The effectiveness of drug sorption is indicated by a decrease in the zeta potential and new bands in the FT-IR spectra. The drug was released from the carrier for 15 h, so all of the drug can be released during circulation in the bloodstream. The release of the drug from the carrier was sustained, and no 'burst release' was observed. The material also released small amounts of zinc, which are important in the treatment of the disease because these ions can prevent some of the adverse effects of chemotherapy. The results obtained are promising and have great application potential.

Chitosan hydrogel modified with lanthanum as a drug delivery system for epigallocatechin gallate: Investigation of hydrogel - drug interaction by FT-IR and Raman spectroscopy.

In the presented work, chitosan hydrogel modified with lanthanum was obtained for the first time. The hydrogel was used as a carrier in the controlled release of epigallocatechin gallate. The work proved the effectiveness of drug sorption by hydrogel and controlled release in simulated body fluids. The drug was released slowly and in a controlled manner from the carrier. The research techniques used in this work (FT-IR spectroscopy and imaging, Raman spectroscopy, SEM/EDS) allowed to confirm the successful retention of EGCG on the hydrogel surface. On the basis of the EDS mapping, it was possible to confirm the even distribution of the lanthanum ions. Using FT-IR imaging, we verified that the drug was evenly distributed on the entire surface of the prepared material. The antifungal effectiveness of the material has been proven on several types of fungi. The research proved that the prepared material is capable of long-term release of the active substance and has antifungal properties. As a result, the prepared material can be successfully used as an implantable hydrogel or a coating in, e.g. titanium implants.

Characterization of Magnesium and Zinc Forms of Sodalite Coatings on Ti6Al4V ELI for Potential Application in the Release of Drugs for Osteoporosis.

Osteoporosis is the most common metabolic disease of the skeletal system and is characterized by impaired bone strength. This translates into an increased risk of low-energy fractures, which means fractures caused by disproportionate force. This disease is quite insidious, its presence is usually detected only at an advanced stage, where treatment with pharmaceuticals does not produce sufficient results. It is obligatory to replace the weakened bone with an implant. For this reason, it is necessary to look at the possibilities of surface modification used in tissue engineering, which, in combination with the drugs for osteoporosis, i.e., bisphosphonates, may constitute a new and effective method for preventing the deterioration of the osteoporotic state. To achieve this purpose, titanium implants coated with magnesium or zinc zeolite were prepared. Both the sorption and release profiles differed depending on the type of ion in the zeolite structure. The successful release of risedronate from the materials at a low level was proven. It can be concluded that the proposed solution will allow the preparation of endoprostheses for patients with bone diseases such as osteoporosis.

Chitosan modified with lanthanum ions as implantable hydrogel for local delivery of bisphosphonates.

Osteoporosis is a disease that affects many people around the world. One group of drugs used to treat it are bisphosphonates. However, they have poor bioavailability and many side effects. Therefore, research around the world is focused on developing bisphosphonate delivery systems. In this paper, we would like to present the design of a hydrogel material with chitosan matrix modified with lanthanum, that could serve as an implantable hydrogel capable of sustained and slow release of Zoledronate. Various research techniques were used to characterize the materials, and the swelling ratio and water solubility were also tested. The conducted research proved that the prepared hydrogel is capable of the long-term release of the Zoledronate. Thanks to this, the prepared material can be successfully used as an implantable hydrogel or a coating on titanium implants for the local delivery of drugs.

Release of drugs used in the treatment of osteoporosis from zeolites with divalent ions-Influence of the type of ion and drug on the release profile.

Bisphosphonates are drugs that are used to treat osteoporosis that causes the low mineral density of the bones. These drugs can be delivered in several ways, but each method has disadvantages. Materials with high potential as carriers of these drugs are zeolites with divalent ions. The aim of this study was to investigate the effect of divalent cations (calcium, magnesium, zinc) and drug type (risedronate, zoledronate) on sorption and release of the drug for osteoporosis. It was proved that drug sorption occurs on all zeolites presented in this work. Risedronate sorption was highest in zinc zeolite and lowest in calcium zeolite. In the case of zoledronate, sorption was most effective in magnesium zeolite and the least effective in zinc zeolite. Very large differences in drug release profiles were also observed. Risedronate was released several times longer than zoledronate. The diversity of the results indicates that the examined materials can be used in different types of drug delivery systems. They can be used, for example, intravenously or in the form of implants due to the different release profiles. Furthermore, the proposed carriers also release magnesium and calcium ions which are used in the prevention of osteoporosis, and zinc ions which have antibacterial properties.

Chitosan - zeolite scaffold as a potential biomaterial in the controlled release of drugs for osteoporosis.

Chitosan scaffolds are a potential material in many biomedical applications. A particularly interesting application is their use in bone tissue engineering. Because of their biocompatibility and nontoxicity, they are an ideal material for this application. What is missing from chitosan scaffolds is controlled drug release. They can obtain this property by adding drug carriers. In this work, chitosan­calcium zeolite scaffolds were prepared and used in the controlled release of the drug for osteoporosis - risedronate. Their properties have been compared with those of the popular chitosan-hydroxyapatite scaffold. The zeolite was evenly distributed throughout the scaffold. More drug was retained on the scaffold with the addition of zeolite compared to that with the hydroxyapatite. The new scaffolds have proven to be able to retain the drug and slowly release it in small doses. The results obtained are promising and show great potential for this material in bone tissue engineering.

Drug distribution evaluation using FT-IR imaging on the surface of a titanium alloy coated with zinc titanate with potential application in the release of drugs for osteoporosis.

The drugs most commonly used in the treatment of osteoporosis are bisphosphonates. This disease results in low mineral density and a weakened bone microstructure. The delivery methods for these drugs have many disadvantages, and new ones are being searched for. In this work, biocompatible zinc titanate coated titanium implants were obtained as potential new carriers for drugs. Such a material will release the drug, and it will have antibacterial properties. Gradual release of the bisphosphonate will have a positive effect on the recovery process and osteointegration. In addition, the drug will be released around the affected bones. The effectiveness of the modification and attachment of the drug was confirmed by SEM, XPS, EDS, FT-IR imaging, and UV-VIS. It was shown that the risedronate could be almost completely released upon contact with body fluids within a week. The drug is evenly distributed over the entire surface of the alloy as confirmed by FT-IR imaging. The results presented in this work will allow for the preparation of endoprostheses that release the drug and have antibacterial properties.

Zeolitic Imidazolate Framework­8 (ZIF-8) modified titanium alloy for controlled release of drugs for osteoporosis.

The aim of this work was to prepare a biocompatible implant material that enables the release of drug for osteoporosis-risedronate. To achieve this goal, a titanium implant coated with a biocompatible Zeolitic Imidazolate Framework 8 (ZIF-8) layer was prepared that promotes osseointegration at the bone-implant interface. The modifications of the titanium alloy as well as sorption and desorption processes were confirmed using a variety of methods: SEM, EDS XPS, and FT-IR imaging (to determine surface modification, drug distribution, and risedronate sorption), and UV-Vis spectroscopy (to determine drug sorption and release profile). Both the ZIF-8 layer and the drug are evenly distributed on the surface of the titanium alloy. The obtained ZIF-8 layer did not contain impurities and zinc ions were strongly bounded by ZIF-8 layer. The ZIF-8 layer was stable during drug sorption. The drug was released in small doses for 16 h, which may help patients recover immediately after surgery. This is the first case of using ZIF-8 on the surface of the titanium alloy as carrier that releases the drug under the influence of body fluids directly at the site of the disease. It is an ideal material for implants designed for people suffering from osteoporosis.

The Effects of Various Food Products on Bisphosphonate's Availability.

The bioavailability of orally administered bisphosphonates is very low (<1%) due to their short absorption window in the proximal duodenum and high affinity for food. Food ingredients are able to bind the drug, but the presence of food extends the residence time of bisphosphonates in the absorption window. Therefore, the main goal of this study is to select a group of food products that are characterized by low binding affinity to bisphosphonates and thus will not reduce their availability upon concomitant administration. For this purpose, a combination of three methods was applied: (1) evaluation of sorption capacity for rows of digested food samples in a simulated intestinal environment; (2) evaluation of drug availability in simulated chyme; and (3) evaluation of drug availability using a simulating needle device. The results indicate that food products such as egg white and white bread are most suitable for consumption during oral bisphosphonate intake.

Controlled release of the drug for osteoporosis from the surface of titanium implants coated with calcium titanate.

The most popular drugs used to prevent osteoporosis that causes low mineral density and weakened microstructure of bones are bisphosphonates. Bisphosphonates can be administered in several ways, but each delivery method has drawbacks. Due to this, new methods of their delivery are being sought. Titanium implants coated with calcium titanate were prepared in this work as carriers for bisphosphonates. Such a modification has been proposed in order to improve the therapeutic properties of the implant. Slow release of the drug at a constant level will positively affect the recovery process and osteointegration. Furthermore, the drug will be slowly released very close to the area affected by osteoporosis. These studies were confirmed, using a variety of methods: EDS and XPS (to examine surface modification and drug sorption), Raman mapping (to proof the presence of the drug on the entire surface of the material) and UV-VIS spectroscopy (to determine bisphosphonate sorption and release profile). It was proved that the active substance (sorbed on the implant) could be completely released upon contact with body fluids within a month. The obtained results will allow for the production of endoprostheses dedicated to patients with osteoporosis in the future.

Determination of bisphosphonates anti-resorptive properties based on three forms of ceramic materials: Sorption and release process evaluation.

There is a strong need to search for more effective compounds with bone anti-resorptive properties, which will cause fewer complications than commonly used bisphosphonates. To achieve this goal, it is necessary to search for new techniques to characterize the interactions between bone and drug. By studying their interaction with hydroxyapatite (HA), this study used three forms of ceramic materials, two of which are bone-stimulating materials, to assess the suitability of new active substances with anti-resorptive properties. In this study, three methods based on HA in loose form, polycaprolactone/HA (a polymer-ceramic materials containing HA), and polymer-ceramic monolithic in-needle extraction (MINE) device (a polymer inert skeleton), respectively, were used. The affinity of risedronate (a standard compound) and sixteen aminomethylenebisphosphonates (new compounds with potential antiresorptive properties) to HA was defined according to the above-mentioned methods. Ten monolithic materials based on 2-hydroxyethyl methacrylate/ethylene dimethacrylate are prepared and studied, of which one was selected for more-detailed further research. Simulated body fluids containing bisphosphonates were passed through the MINE device. In this way, sorption-desorption of bisphosphonates was evaluated using this MINE device. The paper presents the advantages and disadvantages of each technique and its suitability for assessing new active substances. All three methods allow for the selection of several compounds with potentially higher anti-resorptive properties than risedronate, in hope that it reflects their higher bone affinity and release ability.

Silica-filled methacrylic composites with extremely high compressive strength.

SYLOID® 244 has never been applied as a filler in composites with potential dental application. Therefore, the aim of research was to apply this silica in its unmodified and diazonium salt-modified forms in different mass ratios as fillers in light-cured methacrylic composites. The effectiveness of modification process was confirmed with the use of Raman spectroscopy. Methacrylic composites with the modified and unmodified SYLOID® 244, as well as unfilled resin as a control group were prepared. Their basic physicochemical properties, such as depth of cure, mass stability during incubation in saline, flexural and compressive strengths were examined. A positive effect of SYLOID® 244 modification on the properties of the examined composites was also demonstrated. The obtained results proved the high applicability of SYLOID® 244 as a filler in composites with potential dental applications.

Improving the abrasion resistance of Ti6Al4V alloy by modifying its surface with a diazonium salt and attaching of polyurethane.

Commonly used endoprostheses in the orthopedic industry are those made of Ti6Al4V titanium alloy. Unfortunately, this material has low abrasion resistance, and therefore methods of their modification are still sought. A sensible approach is coating the alloy with a layer of a polymer having higher abrasion resistance. The adhesion of polymers to alloy is low, therefore the alloy requires prior modification. In this work, the alloy was modified with three types of diazonium salt and the influence of substituent on the effectiveness of modification was determined. Then, five or ten polyurethane layers were attached to the surface of the modified alloy. Using Raman mapping, the uniform distribution of layers was proved. Layers are stable in simulated human body fluids. The effectiveness of attaching subsequent layers of polyurethane was also confirmed by nanoindentation. The main focus of this work was to improve the wear resistance of the titanium alloy. The obtained results indicate that the titanium alloy with a polyurethane layer has almost ten times lower coefficient of friction compared to pure alloy. Such a low value has not been described in the literature so far. These results are the first step for obtaining endoprostheses with very high abrasion resistance.

Evaluation of the physico-chemical properties of hydrocarbons-exposed bacterial biomass.

In the efforts for the removal of hazardous materials from the environment biological processes are a valuable tool. Although much attention has been paid to the changes in bacteria at the omics level, another, physical-chemical perspective on the issue is essential, as little is known of microbial response to continuous exposition on harmful substances. This study provides in-depth characterization of the physical-chemical parameters of bacterial biomass after hydrocarbons exposure. To provide comparability of the harmful effects of chlorotoluenes and xylenes non-exposed and 12-months hydrocarbons exposed cells were analyzed, using the advanced spectrometric methods, inverse gas chromatography and low-temperature N2 sorption to evaluate acid-base as well as dispersive properties of the studied biomass. Presented results indicate P. fluorescens B01 cells strategy aimed at protecting the cell, thus lowering its' biodegradation efficiency as a result of metabolic stress. The outcome of the study was that prolonged exposure to pollutants might reduce the bioavailability of hydrocarbons to bacteria cells, and consequently decrease the effectiveness of decontamination of polluted sites by indigenous microorganisms.

Inverse gas chromatography in the examination of adhesion between tooth hard tissues and restorative dental materials.

The adhesion is a crucial issue in the bonding of dental restorative materials to tooth hard tissues. A strong and durable bond between artificial and natural materials is responsible for the success of the restoration in the oral cavity; therefore it has to be thoroughly examined before new restorative material is introduced to the market and used clinically. Among all methods used to examine bonding strength, most of them require a large number of healthy teeth to be conducted. In this paper, the bond strength between tooth hard tissues (dentin and enamel) and an exemplary restorative composite was examined with the non-conventional method, i.e. inverse gas chromatography. Dentin and enamel from bovine teeth were separated and subjected to the standard preparation procedure using the 3-component etch-and-rinse commercial bonding system. Tissues, as well as commercial restorative composite, were examined using inverse gas chromatography. The work of adhesion between dentin/enamel and composite was calculated. Obtained results were compared with the values of shear bond strength of six configurations, i.e. etched dentin/enamel-composite, primed dentin/enamel-composite, and bonded dentin/enamel-composite. All obtained results proved that there is a correlation between the values describing bond strength obtained from inverse gas chromatography and direct mechanical tests (shear bond strength tests). It proves that inverse gas chromatography is a powerful perspective tool for the examination of bond strength between tooth hard tissues and potential dental materials without using a large number of health tooth tissues.

Synthesis and Characterization of Low-Cost Cresol-Based Benzoxazine Resins as Potential Binders in Abrasive Composites.

A series of cresol-based benzoxazines were synthesized for potential application as a polymer matrix in abrasive composites. The chemical structures of the obtained benzoxazine resins were investigated in detail using Fourier transform infrared spectroscopy (FTIR) and hydrogen-1 as well as carbon-13 nuclear magnetic resonance spectroscopy (1H NMR, 13C NMR) with an additional analysis using two-dimensional NMR techniques (2D NMR 1H-1H COSY, 1H-13C gHSQC and gHMBC). Structural analysis confirmed the presence of vibrations of -O-C-N- at ~950 cm-1 wavenumber, characteristic for an oxazine ring. The thermal properties of benzoxazine monomers were examined using differential scanning calorimetry (DSC) analysis. The polymerization enthalpy varied from 143.2 J/g to 287.8 J/g. Thermal stability of cresol-based benzoxazines was determined using thermogravimetry (TGA) analysis with additional analysis of the amount of volatile organic compounds (VOC) emitted from the synthesized benzoxazines during their crosslinking by static headspace coupled with gas chromatography technique (HS-GC). The amount of residual mass significantly differed between all synthesized polybenzoxazines in the range from 8.4% to 21.2%. The total VOC emission for benzoxazines decreased by 46-77% in reference to a conventional phenolic binder. The efficiency of abrasive composites with the benzoxazine matrix was evaluated based on abrasion tests. Performed analyses confirmed successful synthesis and proper chemical structure of cresol-based benzoxazines. All the experiments indicated that benzoxazines based on different cresol isomers significantly differ from each other. Good thermal performance and stability of the abrasive composites with the polybenzoxazine matrix and significantly lower VOC emission allow us to state that benzoxazines can be a promising and valuable alternative to the phenolics and a new path for the development of modern, eco-friendly abrasives.