Manufacturing methods, properties, and potential applications in bone tissue regeneration of hydroxyapatite-chitosan biocomposites: A review

Hydroxyapatite (HA) and chitosan (CS) biopolymer are the major materials investigated for biomedical purposes. Both of these components play an important role in the orthopedic field as bone substitutes or drug release systems. Used separately, the hydroxyapatite is quite fragile, while CS mechanical strength is very weak. Therefore, a combination of HA and CS polymer is used, which provides excellent mechanical performance with high biocompatibility and biomimetic capacity. Moreover, the porous structure and reactivity of the hydroxyapatite-chitosan (HA-CS) composite allow their application not only as a bone repair but also as a drug delivery system providing controlled drug release directly to the bone site. These features make biomimetic HA-CS composite a subject of interest for many researchers. Through this review, we provide the important recent achievements in the development of HA-CS composites, focusing on manufacturing techniques, conventional and novel three-dimensional bioprinting technology, and physicochemical and biological properties. The drug delivery properties and the most relevant biomedical applications of the HA-CS composite scaffolds are also presented. Finally, alternative approaches are proposed to develop HA composites with the aim to improve their physicochemical, mechanical, and biological properties.

Synthesis and Evaluation of BSA-Loaded PLGA-Chitosan Composite Nanoparticles for the Protein-Based Drug Delivery System

The purpose of this study was to synthesize composite nanoparticles (NPs) based on poly(d,l-lactic-co-glycolic acid) (PLGA) and chitosan (CS) and evaluate their suitability for the delivery of protein-based therapeutic molecules. Composite NPs possess a unique property which is not exhibited by any other polymer. Unlike other polymers, only the composite NPs lead to improved transfection efficiency and sustained release of protein. The composite NP were prepared by grafting CS on the surface of PLGA NPs through EDC-NHS coupling reaction. The size of bovine serum albumin (BSA)-loaded PLGA NPs and BSA-loaded PLGA-CS composite NPs was 288 ± 3 and 363 ± 4 nm, respectively. The zeta potential of PLGA NPs is -18 ± 0.23, and that of composite particles is 19 ± 0.40, thus confirming the successful addition of CS on the surface of PLGA NPs. Composite NPs were characterized using dynamic light scattering, scanning/transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, release profile, and gel electrophoresis. The encapsulation efficiency of PLGA NPs was 88%. These composite NPs were easily uptaken by the A549 cell line with no or minimal cytotoxicity. The present study emphasizes that the composite NPs are suitable for delivery of BSA into the cells with no cytotoxicity or very little cytotoxicity, while maintaining the integrity of the encapsulated BSA.

Preparation and Surface Characterization of Chitosan-Based Coatings for PET Materials

Poly(ethylene terephthalate)-PET-is one of the most frequently used polymers in biomedical applications. Due to chemical inertness, PET surface modification is necessary to gain specific properties, making the polymer biocompatible. The aim of this paper is to characterize the multi-component films containing chitosan (Ch), phospholipid 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC), immunosuppressant cyclosporine A (CsA) and/or antioxidant lauryl gallate (LG) which can be utilized as a very attractive material for developing the PET coatings. Chitosan was employed owing to its antibacterial activity and also its ability to promote cell adhesion and proliferation favorable for tissue engineering and regeneration purposes. Moreover, the Ch film can be additionally modified with other substances of biological importance (DOPC, CsA and LG). The layers of varying compositions were prepared using the Langmuir-Blodgett (LB) technique on the air plasma-activated PET support. Then their nanostructure, molecular distribution, surface chemistry and wettability were determined by atomic force microscopy (AFM), time-of-flight secondary ion mass spectrometry (TOF-SIMS), X-ray photoelectron spectroscopy (XPS), contact angle (CA) measurements and the surface free energy and its components' determination, respectively. The obtained results show clearly the dependence of the surface properties of the films on the molar ratio of components and allow for a better understanding of the coating organization and mechanisms of interactions at the molecular level both inside the films and between the films and the polar/apolar liquids imitating the environment of different properties. The organized layers of this type can be helpful in gaining control over the surface properties of the biomaterial, thus getting rid of the limitations in favor of increased biocompatibility. This is a good basis for further investigations on the correlation of the immune system response to the presence of biomaterial and its physicochemical properties.

Orally administered docetaxel-loaded chitosan-decorated cationic PLGA nanoparticles for intestinal tumors: formulation, comprehensive in vitro characterization, and release kinetics

Intestinal cancers are the third most lethal cancers globally, beginning as polyps in the intestine and spreading with a severe metastatic tendency. Chemotherapeutic drugs used in the treatment of intestinal tumors are usually formulated for parenteral administration due to poor solubility and bioavailability problems. Pharmaceutically, clinical failure due to a drug's wide biodistribution and non-selective toxicity is one of the major challenges of chemotherapy. In addition, parenteral drug administration in chronic diseases that require long-term drug use, such as intestinal tumors, is challenging in terms of patient compliance and poses a burden in terms of health economy. Especially in the field of chemotherapy research, oral chemotherapy is a subject that has been intensively researched in recent years, and developments in this field will provide serious breakthroughs both scientifically and socially. Development of orally applicable nanodrug formulations that can act against diseases seen in the distant region of the gastrointestinal tract (GIT), such as intestinal tumor, brings with it a series of difficulties depending on the drug and/or GIT physiology. The aim of this study is to develop an oral nanoparticle drug delivery system loaded with docetaxel (DCX) as an anticancer drug, using poly(lactic-co-glycolic acid) (PLGA) as nanoparticle material, and modified with chitosan (CS) to gain mucoadhesive properties. In this context, an innovative nanoparticle formulation that can protect orally administered DCX from GIT conditions and deliver the drug to the intestinal tumoral region by accumulating in mucus has been designed. For this purpose, DCX-PLGA nanoparticles (NPs) and CS/DCX-PLGA NPs were prepared, and their in vitro characteristics were elucidated. Nanoparticles around 250-300 nm were obtained. DCX-PLGA NPs had positive surface charge with CS coating. The formulations have the potential to deliver the encapsulated drug to the bowel according to the in vitro release studies in three different simulated GIT fluids for approximately 72 h. Mucin interaction and penetration into the artificial mucus layer were also investigated in detail, and the mucoadhesive and mucus-penetration characteristics of the formulations were examined. Furthermore, in vitro release kinetic studies of the NPs were elucidated. DCX-PLGA NPs were found to be compatible with the Weibull model, and CS/DCX-PLGA NPs were found to be compatible with the Peppas-Sahlin model. Within the scope of in vitro cytotoxicity studies, the drug-loaded NPs showed significantly higher cytotoxicity than a DCX solution on the HT-29 colon cell line, and CS/DCX-PLGA showed the highest cytotoxicity (p < 0.05). According to the permeability studies on the Caco-2 cell line, the CS/DCX-PLGA formulation increased permeability by 383% compared to free DCX (p < 0.05). In the light of all results, CS/DCX-PLGA NPs can offer a promising and innovative approach as an oral anticancer drug-loaded nanoformulation for intestinal tumors.

Influence of the Impregnation Technique on the Release of Esomeprazole from Various Bioaerogels

The presented study shows the possibility of using bioaerogels, namely neat alginate, pectin, chitosan aerogels, and alginate and pectin aerogels coated with chitosan, as drug delivery systems for esomeprazole. Two different techniques were used for the impregnation of esomeprazole: Supercritical impregnation, and diffusion via ethanol during the sol-gel synthesis. The prepared samples were characterized by employing N₂ adsorption-desorption analysis, TGA/DSC, and FTIR. The achieved loadings were satisfactory for all the tested samples and showed to be dependent on the technique used for impregnation. In all cases, higher loadings were achieved when impregnation via diffusion from ethanol was used. Extensive release studies were performed for all impregnated samples. The in vitro dissolution profiles were found to be dependent on the carrier and impregnation method used. Most importantly, in all cases more controlled and delayed release was achieved with the bioaerogels compared to using pure esomeprazole.

A Green Composite Based on Gelatin/Agarose/Zeolite as a Potential Scaffold for Tissue Engineering Applications

Designing a novel platform capable of providing a proper tissue regeneration environment is a key factor in tissue engineering. Herein, a green composite based on gelatin/agarose/zeolite with pomegranate peel extract was fabricated as an innovative platform for tissue engineering. Gelatin/agarose was loaded with pomegranate peel extract-loaded zeolite to evaluate its swelling behavior, porosity, release rate, and cell viability performance. The composite characteristics were evaluated using XRD and DSC. The hydrogel performance can be adjusted for the desired aim by zeolite content manipulation, such as controlled release. It was shown that the green nanocomposite exhibited proper cellular activity along with a controlled release rate. Moreover, the hydrogel composite’s swelling ratio was decreased by adding zeolite. This study suggested a fully natural composite as a potential biomaterial for tissue engineering, which opens new ways to design versatile hydrogels for the regeneration of damaged tissues. The hydrogel performance can be adjusted specifically by zeolite content manipulation for controlled release.

Metallic-nanoparticle release systems for biomedical implant surfaces: effectiveness and safety

The current focus of bioengineering for implant devices involves the development of functionalized surfaces, bioactive coatings, and metallic nanoparticles (mNPs) with a controlled release, together with strategies for the application of drugs in situ, aiming at reducing infection rates, with an improvement of clinical outcomes. Controversially, negative aspects, such as cytotoxicity, mNP incorporation, bioaccumulation, acquired autoimmunity, and systemic toxicity have gained attention at the same status of importance, concerning the release of mNPs from these surface systems. The balance between the promising prospects of system releasing mNPs and the undesirable long-term adverse reactions require further investigation. The scarcity of knowledge and the methods of analysis of nanoscale-based systems to control the sequence of migration, interaction, and nanoparticle incorporation with human tissues raise hesitation about their efficacy and safety. Looking ahead, this innovative approach requires additional scientific investigation for permitting an evolution of implants without counterpoints, while updating implant surface technologies to a new level of development. This critical review has explored the promising properties of metals at the nano-scale to promote broad-spectrum bacterial control, allowing for a decrease in using systemic antibiotics. Attempts have also been made to discuss the existing limitations and the future challenges regarding these technologies, besides the negative findings that are explored in the literature.

Engineered Site-specific Vesicular Systems for Colonic Delivery: Trends and Implications

Steering drug-loaded, site-specific, coated lipid vesicles to the target receptor sites have the potential of plummeting adverse effects and improving the pharmacological response in diverse pathologies of the large bowel, especially the colon. Colonic delivery via oral route has its own challenges, often governed by several glitches such as drug degradation or absorption in the upper GIT, instability of proteins/peptides due to high molecular weight, and peptidase activity in the stomach. Consequently, colon-specific coated liposomal systems (CSLS) offer a potential alternate for not only site-specificity, but protection from proteolytic activity, and prolonged residence time for greater systemic bioavailability. On the other hand, liposomal delivery via the oral route is also cumbersome owing to several barriers such as instability in GIT, difficulty in crossing membranes, and issues related to production at the pilot scale. New advancements in the field of CSLS have successfully improved the stability and permeability of liposomes for oral delivery via modulating the compositions of lipid bilayers, adding polymers or ligands. Despite this ostensible propitiousness, no commercial oral CSLS has advanced from bench to bedside for targeted delivery to the colon as yet. Nevertheless, CSLS has quite fascinated the manufacturers owing to its potential industrial viability, simplistic and low-cost design. Hence, this review aims to decipher the convolutions involved in the engineering process of industrially viable CSLS for colonic delivery.

Antibacterial potential associated with drug-delivery built TiO2 nanotubes in biomedical implants

The fast evolution of surface treatments for biomedical implants and the concern with their contact with cells and microorganisms at early phases of bone healing has boosted the development of surface topographies presenting drug delivery potential for, among other features, bacterial growth inhibition without impairing cell adhesion. A diverse set of metal ions and nanoparticles (NPs) present antibacterial properties of their own, which can be applied to improve the implant local response to contamination. Considering the promising combination of nanostructured surfaces with antibacterial materials, this critical review describes a variety of antibacterial effects attributed to specific metals, ions and their combinations. Also, it explains the TiO2 nanotubes (TNTs) surface creation, in which the possibility of aggregation of an active drug delivery system is applicable. Also, we discuss the pertinent literature related to the state of the art of drug incorporation of NPs with antibacterial properties inside TNTs, along with the promising future perspectives of in situ drug delivery systems aggregated to biomedical implants.

Chitin/Chitosan: Versatile Ecological, Industrial, and Biomedical Applications

Chitin is a linear polysaccharide of N-acetylglucosamine, which is highly abundant in nature and mainly produced by marine crustaceans. Chitosan is obtained by hydrolytic deacetylation. Both polysaccharides are renewable resources, simply and cost-effectively extracted from waste material of fish industry, mainly crab and shrimp shells. Research over the past five decades has revealed that chitosan, in particular, possesses unique and useful characteristics such as chemical versatility, polyelectrolyte properties, gel- and film-forming ability, high adsorption capacity, antimicrobial and antioxidative properties, low toxicity, and biocompatibility and biodegradability features. A plethora of chemical chitosan derivatives have been synthesized yielding improved materials with suggested or effective applications in water treatment, biosensor engineering, agriculture, food processing and storage, textile additives, cosmetics fabrication, and in veterinary and human medicine. The number of studies in this research field has exploded particularly during the last two decades. Here, we review recent advances in utilizing chitosan and chitosan derivatives in different technical, agricultural, and biomedical fields.

Tacrolimus-Eluting Suture Inhibits Neointimal Hyperplasia: An Experimental In Vivo Study in Rats

OBJECTIVE/BACKGROUND

Neointimal hyperplasia (NIH) remains one of the leading causes of graft failure after vascular anastomoses. Cytotoxic drugs, such as rapamycin and tacrolimus, have been shown to inhibit the development of NIH. In this study, the aim was to test the impact of a sustained releasing tacrolimus-chitosan-eluting suture on the development of NIH in a rat model.

METHODS

After tacrolimus-chitosan coating of a 7/0 polyvinylidene difluoride (PVDF) Trofilen^® suture, the tacrolimus concentration on the coated suture and in vitro release trials were performed spectrophotometrically. Twelve Wistar rats were included. After midline laparotomy, a 7-8 mm longitudinal aortotomy in the infrarenal aorta was made and then closed by a bare 7/0 PVDF (group C, n = 6) and a 7/0 tacrolimus-chitosan coated PVDF suture (0.65 μg/cm tacrolimus [0.9 wt%] + 1.82 μg/cm chitosan [2.28 wt%]) (group T, n = 6). After 1 month, rats were sacrificed and aortotomy sites were examined histologically by ratio of intimal area (including neointima) and immunohistochemically by α-smooth muscle actin (ASMA) and proliferating cell nuclear antigen (PCNA) immunostaining. The PCNA positive cells were indexed to total cell number and expressed as percentage.

RESULTS

In vitro tacrolimus release tests for a 7/0 tacrolimus-chitosan coated PVDF suture were confirmed for 1 month without an initial burst release. Endothelialisation over the aortotomy line occurred in both groups. The area of neointima was significantly reduced in group T compared with group C (ratio 0.22 ± 0.12 vs. 0.42 ± 0.11; p = .017) 1 month post-operatively. Likewise, the percentage of PCNA immunostaining significantly decreased in group C compared with group T (3.83 ± 2.85% vs. 11.17 ± 7.78%; p = .026). The cells constituting NIH were positive for ASMA immunostaining.

CONCLUSIONS

Tacrolimus-chitosan-eluting suture is shown to be an effective way to reduce NIH without interfering with normal endothelialisation.

Establishing Antibacterial Multilayer Films on the Surface of Direct Metal Laser Sintered Titanium Primed with Phase-Transited Lysozyme

Direct metal laser sintering is a technology that allows the fabrication of titanium (Ti) implants with a functional gradation of porosity and surface roughness according to three-dimensional (3D) computer data. The surface roughness of direct metal laser sintered titanium (DMLS-Ti) implants may provide abundant binding sites for bacteria. Bacterial colonization and subsequent biofilm formation can cause unsatisfactory cell adhesion and implant-related infections. To prevent such infections, a novel phase-transited lysozyme (PTL) was utilized as an initial functional layer to simply and effectively prime DMLS-Ti surfaces for subsequent coating with antibacterial multilayers. The purpose of the present study was to establish a surface with dual biological functionality. The minocycline-loaded polyelectrolyte multilayers of hyaluronic acid (HA) and chitosan (CS) formed via a layer-by-layer (LbL) self-assembly technique on PTL-functionalized DMLS-Ti were designed to inhibit pathogenic microbial infections while allowing the DMLS-Ti itself and the modified coatings to retain acceptable biocompatibility. The experimental results indicate that the DMLS-Ti and the hydrogel treated surfaces can inhibit early bacterial adhesion while completely preserving osteoblast functions. This design is expected to gain considerable interest in the medical field and to have good potential for applications in multifunctional DMLS-Ti implants.