Hydroxyapatite/polyurethane composites as promising biomaterials

In Situ Preparation of Composite Scaffolds Based on Polyurethane and Hydroxyapatite Particles for Bone Tissue Engineering

This article details the in situ preparation of composite scaffolds using polyurethane (PU) and HAp (hydroxyapatite), focusing on the unique properties of buriti oil (Mauritia flexuosa L.) applicable to tissue engineering. PU derived from vegetable oils, particularly buriti oil, has shown promise in bone tissue repair due to its rich bioactive compounds. Buriti oil is an excellent candidate for manufacturing these materials as it is an oil rich in bioactive compounds such as carotenoids, tocopherols, and fatty acids, which have antioxidant and anti-inflammatory properties. Furthermore, buriti oil has oleic acid as its principal fatty acid, which has been investigated as an excellent HAp dispersant. This research aimed to synthesize PU scaffolds from a polyol derived from buriti oil and incorporate HAp in different concentrations into the polymeric matrix through in situ polymerization. The chemical composition of the materials obtained, the distribution of hydroxyapatite particles in the polyurethane matrix, and the thermal stability were evaluated using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDS), and thermogravimetry (TGA). In addition, to investigate biocompatibility, MTT tests (3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium) were conducted using rat bone-marrow-derived mesenchymal stem cells (BMMSC). Characterizations confirm the formation of PU and the presence of HAp in the polymeric matrix, and the materials did not show cytotoxicity.

Calcium Orthophosphate (CaPO4) Containing Composites for Biomedical Applications: Formulations, Properties, and Applications

The goal of this review is to present a wide range of hybrid formulations and composites containing calcium orthophosphates (abbreviated as CaPO4) that are suitable for use in biomedical applications and currently on the market. The bioactive, biocompatible, and osteoconductive properties of various CaPO4-based formulations make them valuable in the rapidly developing field of biomedical research, both in vitro and in vivo. Due to the brittleness of CaPO4, it is essential to combine the desired osteologic properties of ceramic CaPO4 with those of other compounds to create novel, multifunctional bone graft biomaterials. Consequently, this analysis offers a thorough overview of the hybrid formulations and CaPO4-based composites that are currently known. To do this, a comprehensive search of the literature on the subject was carried out in all significant databases to extract pertinent papers. There have been many formulations found with different material compositions, production methods, structural and bioactive features, and in vitro and in vivo properties. When these formulations contain additional biofunctional ingredients, such as drugs, proteins, enzymes, or antibacterial agents, they offer improved biomedical applications. Moreover, a lot of these formulations allow cell loading and promote the development of smart formulations based on CaPO4. This evaluation also discusses basic problems and scientific difficulties that call for more investigation and advancements. It also indicates perspectives for the future.

The Application of Hydroxyapatite NPs for Adsorption Antibiotic from Aqueous Solutions: Kinetic, Thermodynamic, and Isotherm Studies

Antibiotic pollution has become a serious concern due to the extensive use of antibiotics, their resistance to removal, and their detrimental effects on aquatic habitats and humans. Hence, developing an efficient antibiotic removal process for aqueous solutions has become vital. Amoxicillin (Amox) is one of the antibiotics that has been efficiently removed from an aqueous solution using hydroxyapatite nanoparticles (HAP NPs). The current study synthesizes and utilizes hydroxyapatite nanoparticles as a cost-effective adsorbent. Adsorbent dose, pH solution, initial Amox concentration, equilibrium time, and temperature are among the factors that have an evident impact on Amox antibiotic adsorption. The (200) mg dose, pH (5), temperature (25) °C, and time (120) min are shown to be the best-optimized values. The nonlinear Langmuir’s isotherm and pseudo-second-order kinetic models with equilibrium capacities of 4.01 mg/g are highly compatible with the experimental adsorption data. The experimental parameters of the thermodynamic analysis show that the Amox antibiotic adsorption onto HAP NPs powder is spontaneous and exothermic.

Hydrophilic competent and enhanced wet-bond strength castor oil-based bioadhesive for bone repair

Bone adhesive has been proved to be a promising alternative in the clinical treatment of bone repairs. However, the problems of unsatisfying bone-bonding strength, especially the bonding of cortical bone in vivo, and blocked bone tissue recovery remain barriers to clinical reparation. Benefit from dopamine-modified castor oil synthesized by an epoxy-modification method, a porous and two-component polyurethane adhesive (PUA) was prepared to overcome the current challenges encountered. The tailored surface morphology and open porosity of the adhesive layer can be obtained to meet the requirements of bone repair by tuning the fraction of the formulation. Furthermore, the incorporation of nano-hydroxyapatite improved the mechanical properties and osteocompatibility of the material. Compared with PUA without catechol groups, the introduction of catechol groups not only increased the adhesive strength from 0.28 ± 0.05 MPa to 0.58 ± 0.06 MPa under wet conditions but also enabled the enrichment of Ca2+ on the adhesive surface to promote bone regeneration. Besides, the cell culture experiments also indicated that PUAs show good biocompatibility and excellent adhesion to stem cells. Given its excellent wet adhesive strength and biocompatibility, this system demonstrated potential applications in orthopedic treatment.

The Effect of Starch and Magnetite on the Physicochemical Properties of Polyurethane Composites for Hyperthermia Treatment

In this study, modified polyurethanes (PUs) with starch and magnetite were synthesized in the form of scaffolds for potential applications in orthopedics. Polyurethanes were synthesized using a one-step method. PU synthesis was carried out using poly(ε-caprolactone) 2000 as soft segments and 4,4 ${}^{\prime }$ -methylenediphenyl diisocyanate (MDI). Various molar ratios of starch and 1,5-pentanediol (PDO) as crosslinker/chain extender were applied, and the effects of incorporating different amounts of magnetite, as well as the role of PDO to starch ratio, were studied. The use of the additive in the form of magnetic particles was to feature the polyurethane materials for use in hyperthermia. The prepared polyurethanes were investigated using Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), thermogravimetry (TG), and dynamic mechanical analysis (DMA) methods. Scanning electron microscopy (SEM)/energy-dispersive X-ray spectroscopy (EDX) analysis and preliminary bioactivity assessment were also performed. The addition of magnetic particles did not cause significant changes in the properties of the obtained materials compared to starch. The tested materials have the potential to be used to fill or replace bone defects in orthopedics, where they can undergo hyperthermia treatment.

Low-Cost and Eco-Friendly Hydroxyapatite Nanoparticles Derived from Eggshell Waste for Cephalexin Removal

This work describes the hydroxyapatite nanoparticle (HAP) preparation from eggshell waste and their application as an adsorbent for Cephalexin (Ceph) antibiotic removal from aqueous solutions. Chemical precipitation with phosphoric acid was used to evaluate the feasibility of calcium oxide for HAP preparation. The structural properties of HAP were characterized by X-ray diffraction, which revealed the formation of the hydroxyapatite crystalline phase formation. In addition, transmitting electron spectroscopy showed an irregular shape with a variation in size. The impact of various experimental conditions on the removal efficiency such as the solution’s pH, contact time, HAP mass, solution temperature, and Ceph concentration were studied. Experimental data showed that HAP could remove most Ceph species from aqueous solutions within 1 h at pH = 7 with 70.70% adsorption efficiency utilizing 50 mg of the HAP. The removal process of Ceph species by HAP was kinetically investigated using various kinetic models, and the results showed the suitability of the pseudo-second-order kinetic model for the adsorption process description. Moreover, the removal process was thermodynamically investigated; the results showed that the removal was spontaneous endothermic and related to the randomness increase. The data confirmed that HAP had high efficiency in removing Ceph antibiotics from an aqueous solution.

Nano-hydroxyapatite as a delivery system: overview and advancements

Nano-hydroxyapatite is being investigated as vital components of implants and dental and tissue engineering devices. It is found as a bone replacement due to its non-toxicity and cytocompatibility with dental tissues and bone. The reality that nanocrystalline hydroxyapatite can be made of porous granules and scaffolds. Additionally, it has a massive loading potential indicating its use as a transporter for drugs or a regulated drug release mechanism in pharmaceutical research. This review aims to present existing nano-hydroxyapatite research developments as a drug carrier employed in bone tissue disorders locally and deliver poorly soluble drugs with reduced bioavailability. We have discussed the nano-hydroxyapatite role in the delivery of drugs (i.e. anti-resorptive, anti-cancer, and antibiotics), proteins, genetic material, and radionuclides.

Stimuli-Responsive Electrospun Piezoelectric Mats of Ethylene-co-vinyl Acetate-Millable Polyurethane-Nanohydroxyapatite Composites

Piezoelectric materials have gained interest among materials scientists as body motion sensors and energy harvesters on account of their fast responsiveness and substantial output signals. In this work, piezoelectric polymer mats have been fabricated from ethylene-co-vinyl acetate-millable polyurethane/nanohydroxyapatite (EVA-MPU/nHA) composite systems by employing the electrospinning technique. The ferro-piezoelectric features of the samples were confirmed from the butterfly loops of electrostatic force microscopy (EFM) amplitude signals as well as through the hysteresis curves of the EFM phase recorded with the assistance of dynamic-contact EFM. Piezoelectric responses of the samples to random finger tapping were evaluated after fabricating a simple device prototype connected to an oscilloscope. The efficacy of the mats to generate a voltage in response to activities such as mechanical bending, movement of throat muscles while drinking, movement of elbow joints, air blowing, and so forth has also been investigated. The results suggest the promising possibility of fabricating user-friendly piezoelectric mats out of the EVA-MPU/nHA system for physiological motion-sensing applications.

A Novel Resorbable Composite Material Containing Poly(ester-co-urethane) and Precipitated Calcium Carbonate Spherulites for Bone Augmentation-Development and Preclinical Pilot Trials

Polyurethanes have the potential to impart cell-relevant properties like excellent biocompatibility, high and interconnecting porosity and controlled degradability into biomaterials in a relatively simple way. In this context, a biodegradable composite material made of an isocyanate-terminated co-oligoester prepolymer and precipitated calcium carbonated spherulites (up to 60% w/w) was synthesized and investigated with regard to an application as bone substitute in dental and orthodontic application. After foaming the composite material, a predominantly interconnecting porous structure is obtained, which can be easily machined. The compressive strength of the foamed composites increases with raising calcium carbonate content and decreasing calcium carbonate particle size. When stored in an aqueous medium, there is a decrease in pressure stability of the composite, but this decrease is smaller the higher the proportion of the calcium carbonate component is. In vitro cytocompatibility studies of the foamed composites on MC3T3-E1 pre-osteoblasts revealed an excellent cytocompatibility. The in vitro degradation behaviour of foamed composite is characterised by a continuous loss of mass, which is slower with higher calcium carbonate contents. In a first pre-clinical pilot trial the foamed composite bone substitute material (fcm) was successfully evaluated in a model of vertical augmentation in an established animal model on the calvaria and on the lateral mandible of pigs.

Hydroxyapatite as a biomaterial - a gift that keeps on giving

The synthetic analogue to biogenic apatite, hydroxyapatite (HA) has a number of physicochemical properties that make it an attractive candidate for diagnosis, treatment of disease and augmentation of biological tissues. Here we describe some of the recent studies on HA, which may provide bases for a number of new medical applications. The content of this review is divided to different medical application modes utilizing HA, including tissue engineering, medical implants, controlled drug delivery, gene therapies, cancer therapies and bioimaging. A number of advantages of HA over other biomaterials emerge from this discourse, including (i) biocompatibility, (ii) bioactivity, (iii) relatively simple synthesis protocols for the fabrication of nanoparticles with specific sizes and shapes, (iv) smart response to environmental stimuli, (v) facile functionalization and surface modification through noncovalent interactions, and (vi) the capacity for being simultaneously loaded with a wide range of therapeutic agents and switched to bioimaging modalities for uses in theranostics. A special section is dedicated to analysis of the safety of particulate HA as a component of parenterally administrable medications. It is concluded that despite the fact that many benefits come with the usage of HA, its deficiencies and potential side effects must be addressed before the translation to the clinical domain is pursued. Although HA has been known in the biomaterials world as the exemplar of safety, this safety proves to be the function of size, morphology, surface ligands and other structural and compositional parameters defining the particles. For this reason, each HA, especially when it comes in a novel structural form, must be treated anew from the safety research angle before being allowed to enter the clinical stage.

The Effect of Chitosan on the Chemical Structure, Morphology, and Selected Properties of Polyurethane/Chitosan Composites

Materials science is an interdisciplinary area of studies. This science focuses on the influence of the physico-chemical properties of materials on their application in human everyday lives. The materials’ synthesis should be developed in accordance with sustainable development. Polyurethanes (PUR) represent a significant consumption of plastic in the world. Modification of PUR, e.g., with polysaccharide of natural origin (chitosan, Chit), should have a positive effect on their functional properties and degradability in the natural environment. The basic parameters affecting the scope and direction of changes are the size and quantity of the chitosan particles. The impact assessment of chitosan on the chemical structure, morphology, thermal properties, crystallinity, mechanical properties, flammability, water sorption, adsorption properties, degradability, and biological activity of PUR/Chit composites (without other additives) is discussed in this article. To the best of our knowledge, recent literature does not contain a study discussing the direct impact of the presence of chitosan in the structure of PUR/Chit composite on its properties, regardless of the intended uses. This paper provides an overview of publications, which presents the results of a study on the effect of adding chitosan in polyurethane/chitosan composites without other additives on the properties of polyurethane.

Ecofriendly Reduction of Methylene Blue with Polyurethane Catalyst

A number of physical, chemical, and biological technologies have been developed to address the issue of synthetic dyes in wastewater. One of the important chemical methods involves reduction of these stringent pollutants into less hazardous products. In this study, a cross-linked polyurethane foam (CPUF) was prepared from toluene diisocyanate (TDI), tetraethylenepentamine (TEPA), and polycaprolactone diol (PCL; Mw: 1000 g/mole). To avoid harmful reducing agents, ecofriendly reduction of methylene blue (MB) was executed with CPUF as catalyst where ascorbic acid and fresh juice extracts were applied as reducing agents. The FTIR and SEM analysis confirmed the chemical composition and porous morphology of CPUF, respectively. The 100% reduction of MB was recorded in just 15 minutes with ascorbic acid and CPUF, while similar result was obtained in 37 minutes in blank experiment composed of only MB and ascorbic acid. Thus, catalytic role of CPUF in reduction process was proved. Fresh fruit extracts also participated in the reduction process, but rate of reaction was accelerated in the presence of CPUF. The reusability study of the catalyst supported its stability and efficiency. All the successful reduction processes followed 1st-order kinetics with highest apparent rate constant for ascorbic acid. Furthermore, phytotoxicity evaluation proved safe reduction of MB with 60% germination index. Hence, it can be concluded that catalytic role of CPUF has been established with safe and biodegradable reducing agents which can be extended to other redox processes.