Aquasomes are self-assembling nanoparticle drug carrier systems composed of three layers: a ceramic core, an oligomer coat, and a loaded biochemically active molecule. Aquasomes are utilized for targeted drug delivery to achieve specific therapeutic effects, and are biocompatible, biodegradable, and stable. Due to their structure, aquasomes are capable of delivering several types of substrates, and can be used for applications such as delivery of antigens, insulin, and hemoglobin.
Aquasomes were first investigated by Kossovsky et al. in 1996 in experiments proposing their use in antigen delivery, drug delivery, and hemoglobin delivery systems. [2] This initial research described aquasomes as self-assembling, with a novel surface modification process allowing the immobilization of drugs on the surface. [2] The research was intended to address the molecular denaturation of polypeptide pharmaceuticals. [2] Kossovsky et al. suggested that this system would be able to combat physical and chemical degradative agents affecting bioactive molecules while preserving the molecular structure of the drug. [2]
Since this initial exploration, the understanding of the composition and applications of aquasomes has increased. After each individual layer is synthesized, aquasomes self-assemble into triple-layered particles. The tri-layer structure enables aquasomes to deliver and release poorly soluble drugs in a controlled manner. Delivery of these poorly soluble drugs within aquasomes increases their solubility, bioavailability, and stability. These drugs are adsorbed onto the surface of the aquasome, forming its third layer, which confers bioactive properties to the aquasome.
Aquasomes form a three-layered structure, made of a polyhydroxy oligomer coated core upon which the drug is loaded. The biochemically active molecules are able to interact with the coated core through different Van der Waal forces, entropic forces, and ionic and non-covalent bonds. [3] The structure of aquasomes enables them to carry a variety of substrates (chemicals), facilitating applications such as protein and peptide delivery and protection, and the delivery of nucleic acids for gene therapy applications. [1]
Aquasomes’ solid core, made of ceramic or polymeric material, is attributed to the structural stability of the nanoparticle itself, and can result in improved solubility and biocompatibility of the drug. [1] Different core designs have also been shown to affect the controlled release properties of the drug molecule. A commonly used core material is the ceramic calcium phosphate, which naturally occurs in the body. [1] Hydroxyapatite, which is found in bone, is another commonly used core material. Hydroxyapatite cores have been shown to contribute to targeted delivery of encapsulated hepatitis B antigens intracellularly. [1]
The second layer of aquasomes is the carbohydrate coat, onto which the drug is adsorbed. Due to carbohydrate’s action as a dehydroprotectant,[ definition needed ] it has been shown to function as a natural stabilizer to preserve the conformation (shape) of soft drugs. [1] The dehydroprotectant property of the carbohydrate coat also enables protection of the biochemically active molecule from dehydration and protein degradation. [1]
The size of aquasomes ranges from 60 to 300 nanometers, hence their characterization as a nanoparticle drug carrier. [2] The nanoscale of aquasomes gives them a high surface area to volume ratio. The smaller the core, the higher the surface area to volume ratio, which increases the drug loading capacity of the aquasome. [3] Aquasomes possess water-like properties due to the presence of the carbohydrate coating, enabling them to protect and preserve fragile biological molecules. The size of aquasome particles increases as a function of the ratio between the concentration of the core to the coat due to the availability of free surface core particles for the coating material. [1]
The self-assembly process of aquasomes into their tri-layer structure is achieved by non-covalent and ionic bonds, along with physicochemical properties of their components. Calcium phosphate nanoparticles are formed before the carbohydrate coat is adsorbed onto the surface of the core through electrostatic interactions. Layers are then added to the structure to achieve desired size, while crosslinked polymers aid in further stabilization. The sonication process during the reaction of disodium hydrogen phosphate and calcium chloride to prepare calcium phosphate impacts the self-assembly process of aquasomes by increasing surface free energy of the core prepared. This assembly process allows the design of aquasomes for specific drug delivery applications. [3]
The structure of aquasomes can contribute to controlled drug release, drug stability, and intracellular targeting of the drug. Other commonly used nanoparticle drug delivery systems include niosomes, liposomes, and vesosomes, the compositions of which contribute to different properties of the resulting nanoparticle compared to aquasomes. Niosomes are composed of non-ionic surfactants and bilayer structures, allowing them to encapsulate hydrophilic and hydrophobic drugs. Liposomes are composed of phospholipids and a similar bilayer structure to niosomes, and can deliver toxic or poorly soluble drugs. Vesosomes have a core-shell structure similar to aquasomes, but contain a lipid bilayer core and a polymer shell, while aquasomes consist of a ceramic or polymeric core and a carbohydrate coat. Vesosomes are used for encapsulating imaging agents and aiding in imaging techniques such as MRI. [4] [5]
The three major units of aquasomes are fabricated together according to self-assembly, a thermodynamically driven process that organizes subunits of a system in a manner that results in the lowest Gibbs free energy available, known as ΔG. Self-assembly as a mixing process offers high accuracy and control over sizes on the nanometer scale, which is especially relevant for aquasomes, which exist on this size scale. The three layers of aquasomes can be synthesized differently using a variety of techniques depending on the intended functions or desired therapeutic effects. [1] The general scheme of aquasome fabrication involves a sequential synthesis of a nanocrystalline core, followed by a polyhydroxy coating, and finished with integration of bioactive molecules. Throughout this process, several intermittent steps are included that involve selective filtering and purification to remove byproducts while isolating the desired products for further processing. [1]
The core of an aquasome can be made from either ceramic or polymeric materials. Examples of such polymers include acrylates and gelatin. However, because ceramic materials are more ordered due to their naturally occurring crystalline structure, they are more often preferred as the material type for the core. [1] Some of the most common ceramic materials used in the formation of an aquasome core include tin oxide, calcium phosphate, and even diamond. Another characteristic that ceramic materials provide is enhanced binding of the carbohydrate layer due to the high surface energy present on the orderly surface. The binding affinity of the carbohydrate layer also reduces surface tension for its bond to the ceramic core. [2] The first aquasomes fabricated with a nanocrystalline core using ceramic material are detailed in Kossovsky et al. in 1996. [2] Calcium phosphate ceramic nanoparticles (brushite) were first prepared via the method of solution precipitation and sonication. [2] Precipitation methods are the most common techniques employed when synthesizing the core of an aquasome as they offer control over the homogeneity and purity of the precipitated products, which are important design features in the core structure. [1] Once the cores are prepared, they are separated by centrifugation and then washed to remove any salt byproducts from the solution precipitation process. Finally, the washed cores are passed through a Millipore filter to selectively isolate core particles of a certain size. [2]
After synthesizing and purifying the core, the carbohydrate layer is added to its surface. Common coating materials are typically polyhydroxy oligomers such as cellobiose, citrate, lactose, and sucrose. [2] This layer seems to be important for the properties of aquasomes, as it influences several drug characteristics including adsorption, molecular stability, and conformation (shape), and acts as a dehydroprotectant. [1] [ definition needed ] The addition of the carbohydrate layer to the surface of the nanocrystalline core is commonly carried out by passive adsorption through incubation[ clarification needed ] and sonication. Similar to the processing of the core, the carbohydrate layer is subjected to centrifugation, washing, and further sonification followed by heated air drying. [1]
Finally, the bioactive molecule of interest is loaded into the carbohydrate layer. This process typically occurs through either lyophilization or passive adsorption, and the fully functionalized aquasome is then characterized. [1]
Solution precipitation as a core synthesis technique produces homogenous-sized nanoparticles, which can be advantageous in controlling specific physical properties such as surface tension and packing density of the atoms in a crystalline lattice structure. [1] The most common methods of characterizing nanoparticle size distribution and morphology of the core in aquasomes include scanning electron microscopy (SEM) and transmission electron microscopy (TEM).[ citation needed ] In a study by Kommimeni et al. in 2012, researchers employed TEM to verify that the ceramic particles were spherical and also in the acceptable nano-range for aquasomes. [6] The carbohydrate coating size can also be characterized using SEM and TEM, but Fourier-transform infrared spectroscopy (FTIR) is commonly utilized to check for the presence of the coat.[ citation needed ] In a study by Kommimeni et al. in 2020, FTIR was used to confirm the presence of the coating by analyzing the IR spectra bands that correspond to the functional groups of either the core or the sugar coat. [6]
The bioactive drug loaded onto the aquasome can be characterized in a variety of ways depending on the molecular classification of the drug. In Kossovsky et al. in 1996, which studied the effect of insulin as the bioactive drug of interest, immunogold labeling was employed. Through this technique, the different binding efficiencies of carbohydrate coatings for insulin were able to be observed. [2]
The structure of aquasomes enables dual drug delivery, or the delivery of two drugs simultaneously. This practice aims to enhance the therapeutic efficiency and reduce the side effects of the drugs delivered. Such systems can be useful in treating patients suffering from multiple diseases. Challenges in dual drug delivery include independently controlling release rates of each of the drugs loaded in the system. In a 2019 study by Damera et al., aquasomes were used to deliver bovine serum albumin (BSA) in combination with one of three therapeutic drugs (Coumarin 153, Warfarin, and Ibuprofen), allowing release of a bioactive molecule and a hydrophobic drug simultaneously. [7] Damera et al. suggested that dual drug delivery was enabled by the bioactive molecule layer of the aquasome being BSA. This BSA layer interacted with the hydrophobic therapeutic drugs, and the strength of the binding interactions was shown to affect the release behaviors of the drugs. Dual drug delivery with aquasomes thus shows promise for treatment of patients with coexisting diseases alongside hypoalbuminemia, as the albumin from BSA can treat the hypoalbuminemia while the additional drug treats the disease. [7]
Aquasomes have been explored as carriers for hemoglobin throughout the body. In a 2002 study by Khopade, Khopade, and Jain, aquasomes were used to act as red blood cell substitutes with hemoglobin attached to the oligomer surface. Aquasomes in this application demonstrated minimal toxicity while obtaining a hemoglobin content of 80%, supplying blood and oxygen in a manner similar to regular red blood cells. [8] Hemoglobin aquasomes with spherical hydroxyapatite cores have been shown to retain oxygen-affinity and cooperativity for 30 days in rats in vivo, causing no red blood cell hemolysis or blood coagulation, demonstrating potential capability as effective oxygen transporters. Additionally, aquasomes protected hemoglobin from degradation while maintaining hemoglobin function. Future exploration of aquasomes as hemoglobin carriers may explore controlled release of the aquasomes themselves to mimic typical oxygen release properties to aid in biomedical applications that require specific targeting and delivery of hemoglobin. [8]
Aquasomes with calcium phosphate ceramic cores may be useful for the pharmaceutical administration of substrates such as insulin where drug action is conformationally specific. In a 2000 study by Cherian et al., disaccharides such as trehalose were used to coat the core before insulin was loaded onto the coated cores via adsorption. [9] Albino rats were used as test subjects to test these aquasome insulin formulations, and the efficiency of different carbohydrate coat molecules on the aquasome was explored. Pyridoxal-5-phosphate-coated particles were shown to lower blood glucose levels more efficiently when compared to trehalose- or cellobiose-coated particles, which may be due to their differences in structural stability. [9] The use of these nanoparticles for the delivery of insulin in vivo in rabbits demonstrated that insulin-bearing aquasomes showed slower release and prolonged activity compared to standard insulin solution. [9] Similar to their role in carrying hemoglobin, the carbohydrate layer of aquasomes may be responsible for the ability to protect insulin from degradation when injected subcutaneously as in the albino rats tested. Aquasomes were also shown to release insulin in controlled manners, mimicking the typical release of insulin from the pancreas. [9]
A potential challenge of aquasome-based drug delivery could be toxicity due to burst release of drugs if poorly absorbed on the carbohydrate coat. [1] Aquasomes can also be expensive to formulate, particularly due to their step-by-step synthesis. Careful attention is needed during aquasome production to tune the thickness of each layer, and leaching and aggregation may occur during prolonged storage of aquasomes. A physiological challenge aquasomes present is that upon their entry into the bloodstream, they may be taken up nonspecifically,[ definition needed ] leading to opsonization and phagocytic clearance by the immune system. To prevent this, aquasome surfaces can be coated with polyethylene glycol (PEG) to block opsonin binding through steric hindrance; however, the effect of PEGylation on aquasome drug release has not been sufficiently explored to enable clinical applications. [1] Polymer degradation in different physiological environments can change the stability and drug loading of aquasomes over time, as their surface properties directly impact drug release. Aquasomes may also be challenging to scale up and prepare as it is difficult to ensure consistent formulation quality. More research is needed to demonstrate both the efficiency and safety of aquasomes in clinical use. [1]
Further advances in aquasome research require additional investigation of their in vivo drug release and targeting. Applications such as delivery of dithranol for the treatment of psoriasis and oral delivery of bromelain for the treatment of inflammatory diseases such as cancer show promising results in vitro and ex vivo. However, such applications have been unexplored in vivo, limiting their clinical use. Applications using aquasomes as carriers of hemoglobin, vaccines, and insulin have been tested in vivo in small animal models such as rats, mice, and rabbits, but current literature lacks in vivo testing in more advanced animal models, preventing their use as treatments for human conditions. Aquasomes are promising drug delivery mechanisms due to their ability to stabilize and transport a variety of substrates while allowing for controlled drug release. Prior to expanding the clinical applications of aquasomes, the gap existing in current literature will need to be filled by further investigating immune clearance of aquasomes, exploring additional surface modifications such as PEGylation, and expanding in vivo drug testing. [1]
Microencapsulation is a process in which tiny particles or droplets are surrounded by a coating to give small capsules, with useful properties. In general, it is used to incorporate food ingredients, enzymes, cells or other materials on a micro metric scale. Microencapsulation can also be used to enclose solids, liquids, or gases inside a micrometric wall made of hard or soft soluble film, in order to reduce dosing frequency and prevent the degradation of pharmaceuticals.
Dendrimers are highly ordered, branched polymeric molecules. Synonymous terms for dendrimer include arborols and cascade molecules. Typically, dendrimers are symmetric about the core, and often adopt a spherical three-dimensional morphology. The word dendron is also encountered frequently. A dendron usually contains a single chemically addressable group called the focal point or core. The difference between dendrons and dendrimers is illustrated in the top figure, but the terms are typically encountered interchangeably.
Electrophoretic deposition (EPD), is a term for a broad range of industrial processes which includes electrocoating, cathodic electrodeposition, anodic electrodeposition, and electrophoretic coating, or electrophoretic painting. A characteristic feature of this process is that colloidal particles suspended in a liquid medium migrate under the influence of an electric field (electrophoresis) and are deposited onto an electrode. All colloidal particles that can be used to form stable suspensions and that can carry a charge can be used in electrophoretic deposition. This includes materials such as polymers, pigments, dyes, ceramics and metals.
Bioactive glasses are a group of surface reactive glass-ceramic biomaterials and include the original bioactive glass, Bioglass. The biocompatibility and bioactivity of these glasses has led them to be used as implant devices in the human body to repair and replace diseased or damaged bones. Most bioactive glasses are silicate-based glasses that are degradable in body fluids and can act as a vehicle for delivering ions beneficial for healing. Bioactive glass is differentiated from other synthetic bone grafting biomaterials, in that it is the only one with anti-infective and angiogenic properties.
Nanochemistry is an emerging sub-discipline of the chemical and material sciences that deals with the development of new methods for creating nanoscale materials. The term "nanochemistry" was first used by Ozin in 1992 as 'the uses of chemical synthesis to reproducibly afford nanomaterials from the atom "up", contrary to the nanoengineering and nanophysics approach that operates from the bulk "down"'. Nanochemistry focuses on solid-state chemistry that emphasizes synthesis of building blocks that are dependent on size, surface, shape, and defect properties, rather than the actual production of matter. Atomic and molecular properties mainly deal with the degrees of freedom of atoms in the periodic table. However, nanochemistry introduced other degrees of freedom that controls material's behaviors by transformation into solutions. Nanoscale objects exhibit novel material properties, largely as a consequence of their finite small size. Several chemical modifications on nanometer-scaled structures approve size dependent effects.
Nanofabrics are textiles engineered with small particles that give ordinary materials advantageous properties such as superhydrophobicity, odor and moisture elimination, increased elasticity and strength, and bacterial resistance. Depending on the desired property, a nanofabric is either constructed from nanoscopic fibers called nanofibers, or is formed by applying a solution containing nanoparticles to a regular fabric. Nanofabrics research is an interdisciplinary effort involving bioengineering, molecular chemistry, physics, electrical engineering, computer science, and systems engineering. Applications of nanofabrics have the potential to revolutionize textile manufacturing and areas of medicine such as drug delivery and tissue engineering.
Nanotechnology is impacting the field of consumer goods, several products that incorporate nanomaterials are already in a variety of items; many of which people do not even realize contain nanoparticles, products with novel functions ranging from easy-to-clean to scratch-resistant. Examples of that car bumpers are made lighter, clothing is more stain repellant, sunscreen is more radiation resistant, synthetic bones are stronger, cell phone screens are lighter weight, glass packaging for drinks leads to a longer shelf-life, and balls for various sports are made more durable. Using nanotech, in the mid-term modern textiles will become "smart", through embedded "wearable electronics", such novel products have also a promising potential especially in the field of cosmetics, and has numerous potential applications in heavy industry. Nanotechnology is predicted to be a main driver of technology and business in this century and holds the promise of higher performance materials, intelligent systems and new production methods with significant impact for all aspects of society.
Mucoadhesion describes the attractive forces between a biological material and mucus or mucous membrane. Mucous membranes adhere to epithelial surfaces such as the gastrointestinal tract (GI-tract), the vagina, the lung, the eye, etc. They are generally hydrophilic as they contain many hydrogen macromolecules due to the large amount of water within its composition. However, mucin also contains glycoproteins that enable the formation of a gel-like substance. Understanding the hydrophilic bonding and adhesion mechanisms of mucus to biological material is of utmost importance in order to produce the most efficient applications. For example, in drug delivery systems, the mucus layer must be penetrated in order to effectively transport micro- or nanosized drug particles into the body. Bioadhesion is the mechanism by which two biological materials are held together by interfacial forces. The mucoadhesive properties of polymers can be evaluated via rheological synergism studies with freshly isolated mucus, tensile studies and mucosal residence time studies. Results obtained with these in vitro methods show a high correlation with results obtained in humans.
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Bioceramics and bioglasses are ceramic materials that are biocompatible. Bioceramics are an important subset of biomaterials. Bioceramics range in biocompatibility from the ceramic oxides, which are inert in the body, to the other extreme of resorbable materials, which are eventually replaced by the body after they have assisted repair. Bioceramics are used in many types of medical procedures. Bioceramics are typically used as rigid materials in surgical implants, though some bioceramics are flexible. The ceramic materials used are not the same as porcelain type ceramic materials. Rather, bioceramics are closely related to either the body's own materials or are extremely durable metal oxides.
Octacalcium phosphate (sometimes referred to as OCP) is a form of calcium phosphate with formula Ca8H2(PO4)6·5H2O. OCP may be a precursor to tooth enamel, dentine, and bones. OCP is a precursor of hydroxyapatite (HA), an inorganic biomineral that is important in bone growth. OCP has garnered lots of attention due to its inherent biocompatibility. While OCP exhibits good properties in terms of bone growth, very stringent synthesis requirements make it difficult for mass productions, but nevertheless has shown promise not only in-vitro, but also in in-vivo clinical case studies.
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Ceramic nanoparticle is a type of nanoparticle that is composed of ceramics, which are generally classified as inorganic, heat-resistant, nonmetallic solids that can be made of both metallic and nonmetallic compounds. The material offers unique properties. Macroscale ceramics are brittle and rigid and break upon impact. However, Ceramic nanoparticles take on a larger variety of functions, including dielectric, ferroelectric, piezoelectric, pyroelectric, ferromagnetic, magnetoresistive, superconductive and electro-optical.
A simulated body fluid (SBF) is a solution with an ion concentration close to that of human blood plasma, kept under mild conditions of pH and identical physiological temperature. SBF was first introduced by Kokubo et al. in order to evaluate the changes on a surface of a bioactive glass ceramic. Later, cell culture media, in combination with some methodologies adopted in cell culture, were proposed as an alternative to conventional SBF in assessing the bioactivity of materials.
Bioactive glasses have been synthesized through methods such as conventional melting, quenching, the sol–gel process, flame synthesis, and microwave irradiation. The synthesis of bioglass has been reviewed by various groups, with sol-gel synthesis being one of the most frequently used methods for producing bioglass composites, particularly for tissue engineering applications. Other methods of bioglass synthesis have been developed, such as flame and microwave synthesis, though they are less prevalent in research.
Bovine submaxillary mucin (BSM) coatings are a surface treatment provided to biomaterials intended to reduce the growth of disadvantageous bacteria and fungi such as S. epidermidis, E. coli, and Candida albicans. BSM is a substance extracted from the fresh salivary glands of cows. It exhibits unique physical properties, such as high molecular weight and amphiphilicity, that allow it to be used for many biomedical applications.
As with any material implanted in the body, it is important to minimize or eliminate foreign body response and maximize effectual integration. Neural implants have the potential to increase the quality of life for patients with such disabilities as Alzheimer's, Parkinson's, epilepsy, depression, and migraines. With the complexity of interfaces between a neural implant and brain tissue, adverse reactions such as fibrous tissue encapsulation that hinder the functionality, occur. Surface modifications to these implants can help improve the tissue-implant interface, increasing the lifetime and effectiveness of the implant.
Nanocomposite hydrogels are nanomaterial-filled, hydrated, polymeric networks that exhibit higher elasticity and strength relative to traditionally made hydrogels. A range of natural and synthetic polymers are used to design nanocomposite network. By controlling the interactions between nanoparticles and polymer chains, a range of physical, chemical, and biological properties can be engineered. The combination of organic (polymer) and inorganic (clay) structure gives these hydrogels improved physical, chemical, electrical, biological, and swelling/de-swelling properties that cannot be achieved by either material alone. Inspired by flexible biological tissues, researchers incorporate carbon-based, polymeric, ceramic and/or metallic nanomaterials to give these hydrogels superior characteristics like optical properties and stimulus-sensitivity which can potentially be very helpful to medical and mechanical fields.
Nanoparticle drug delivery systems are engineered technologies that use nanoparticles for the targeted delivery and controlled release of therapeutic agents. The modern form of a drug delivery system should minimize side-effects and reduce both dosage and dosage frequency. Recently, nanoparticles have aroused attention due to their potential application for effective drug delivery.
Dextran drug delivery systems involve the use of the natural glucose polymer dextran in applications as a prodrug, nanoparticle, microsphere, micelle, and hydrogel drug carrier in the field of targeted and controlled drug delivery. According to several in vitro and animal research studies, dextran carriers reduce off-site toxicity and improve local drug concentration at the target tissue site. This technology has significant implications as a potential strategy for delivering therapeutics to treat cancer, cardiovascular diseases, pulmonary diseases, bone diseases, liver diseases, colonic diseases, infections, and HIV.