Colloidal Dispersions Overview

Colloids that have a strong attraction to the dispersing medium, forming a stable suspension.

Colloids that have a weak attraction to the dispersing medium, making them less stable and prone to aggregation.

Molecules that have both hydrophilic (water-loving) and hydrophobic (water-fearing) regions, often forming aggregates in water.

Colloids formed spontaneously due to interactions between particles and the dispersing medium.

A substance that forms a lyophilic colloid in one solvent may not do so in another solvent due to differences in interactions.

Lyophilic colloids are not limited to water as the dispersing medium. Other polar solvents are also suitable.

Hydrophilic colloids are typically formed in polar solvents like water, while hydrophobic colloids form in non-polar solvents.

Insoluble particles that have a strong attraction to the solvent can form hydrophilic colloids. They don't dissolve but remain dispersed with a layer of solvent molecules around them.

Hydrophilic colloids are insoluble but extensively solvated particles dispersed in a liquid medium. They have a strong attraction to water, causing them to swell and spontaneously break into particles with colloidal dimensions.

Each particle in a hydrophilic colloid is made from a single molecule.

Lyophobic colloids are particles that have little to no affinity for their dispersion medium. They require specific methods to reduce particle size to the colloidal range.

Lyophobic colloids need stabilizers like surfactants to stay dispersed, as they are not naturally hydrated by their dispersion medium.

Intravenous fat emulsions form lyophilic colloids.

Micelles are spherical aggregates of amphiphilic molecules, like surfactants, that form in aqueous solutions.

The core of a micelle formed in an aqueous dispersion medium is typically hydrophobic, as it attracts and encapsulates nonpolar substances.

Micelles are dynamic structures that can grow and break down, depending on the concentration of the amphiphilic molecules.

The concentration of monomer at which micelles begin to form in an aqueous solution.

Amphiphiles above the CMC will primarily aggregate to form micelles in the bulk phase of the solution, rather than staying at the air-water interface.

Below the CMC, the surface tension of the solution is significantly reduced due to the amphiphiles forming a layer at the air-water interface.

The solubility of water-insoluble substances, or 'solubilizates,' increases significantly above the CMC, as micelles can effectively encapsulate and solubilize these compounds.

The process by which a substance, typically insoluble in a particular solvent, is dissolved by the formation of micelles.

The core of a micelle is a hydrophobic environment, formed by the inward-facing hydrocarbon tails of the amphiphilic molecules. This hydrophobic core is where nonpolar solubilizates reside.

Polar solubilizates, with some water affinity, tend to reside in the outer region of the micelle, where the polar heads of the amphiphiles are exposed to the aqueous environment.

Amphipathic solubilizates, with both polar and nonpolar regions, are typically found in a transition zone between the hydrophobic core and the hydrophilic outer region of the micelle.

A reduction in the concentration of surfactants in a system can lead to the precipitation of solubilizate, which is the substance being dissolved.

In Adult Infuvite Multiple Vitamins for Infusion, vitamin A palmitate is solubilized by micelles formed by the inactive ingredients vitamin K1, alpha-tocopherol acetate, and cholecalciferol.

Microemulsions are unique for their spontaneous formation, physical stability, and high drug solubilization capacity.

Microemulsions are thermodynamically stable and do not require external energy to maintain their stability.

Microemulsions can effectively solubilize lipophilic drugs due to their small droplet size and large surface area.

Microemulsions typically use two surfactants to reduce the interfacial tension between the oil and water phases.

The amount of surfactants in a microemulsion is relatively large to ensure stability and proper formation of the small droplets.

Microemulsions are formed spontaneously without the need for external energy input.

The shape of a molecule, specifically whether it's conical (single tail) or cylindrical (two tails), determines if it forms micelles or liposomes. Conical molecules form micelles, while cylindrical molecules form liposomes.

The critical packing parameter (CPP) is a key factor in determining if a molecule forms micelles or liposomes. It's a ratio that considers the hydrophobic tail volume, hydrophilic head area, and tail length.

Drug release from liposomes often involves interactions with cells, including passive diffusion, absorption through membranes, and endocytosis.

Enhanced permeability and retention (EPR) effects are crucial for drug release from liposomes. These effects involve the accumulation of drugs at the target site and their retention.

Liposomes, after intravenous injection, circulate in the bloodstream and their fate depends on factors like size, charge, lipid composition, and surface modifications.

The Mononuclear Phagocyte System (MPS), mainly macrophages in the liver and spleen, rapidly clears unmodified liposomes from the bloodstream.

The half-life of liposomes in the bloodstream is usually minutes to hours, and MPS uptake often limits their circulation time.

While MPS uptake can reduce drug availability for targeted areas, it can also be beneficial in treating MPS-related diseases.

Microemulsions are thermodynamically stable mixtures of oily and aqueous phases stabilized by surfactants, forming a single-phase system. They have a small droplet size (less than 100 nm) and spontaneously form due to low interfacial tension and precise formulation.

Microemulsions are preferred for lipophilic drugs due to their compatibility with the oil phase, allowing for efficient drug solubilization.

Liposomes are spherical vesicles composed of one or more phospholipid bilayers encapsulating an aqueous core. They are used for drug delivery due to their ability to encapsulate both hydrophilic and hydrophobic drugs.

Multilamellar vesicles (MLV) have multiple concentric phospholipid bilayers, offering high stability but lower drug encapsulation efficiency. Large unilamellar vesicles (LUV) have a single bilayer and offer good encapsulation efficiency for hydrophilic drugs but are less stable.

Small unilamellar vesicles (SUV) have a single bilayer and are smaller than LUVs, facilitating tissue penetration and prolonged circulation. However, they can be unstable due to their small size.

Cholesterol plays a role in liposome structure by contributing rigidity to the bilayer, reducing permeability and stabilizing the vesicle.

Liposomes can accommodate both water-soluble and lipid-soluble drugs. Water-soluble drugs reside in the aqueous core, while lipid-soluble drugs are located within the lipid bilayers.

Factors like the chemical structure of the molecule (hydrophilic vs. hydrophobic), its concentration, and the presence of surfactants and other molecules in the environment determine whether a molecule will form micelles or liposomes.

Dispersion systems consist of dispersed particles in a continuous phase, while colloidal systems are a type of dispersion where particles are between 1-1000nm in size.

Colloidal particles have a much larger surface area compared to the same volume of larger particles. This is due to their smaller size and higher surface-to-volume ratio.

Lyophilic colloids have a strong attraction to the dispersion medium, while lyophobic colloids have a weak attraction. Lyophilic colloids are spontaneously formed and covered with a solvent sheath.

The shape and size of colloidal particles affect their properties like surface area, reactivity, stability, and electrical behavior.

Liposomes are spherical vesicles made of one or more phospholipid bilayers, encapsulating an aqueous core. They are used for drug delivery due to their ability to encapsulate both hydrophilic and hydrophobic drugs.

The critical packing parameter (CPP) determines whether a molecule forms micelles or liposomes. A conical molecule forms micelles, while a cylindrical molecule forms liposomes.

The solubility of water-insoluble substances dramatically increases above the CMC, as micelles effectively encapsulate and solubilize these substances in their hydrophobic core.

The main pharmaceutical applications of colloidal dispersion systems include drug delivery, solubilization of poorly soluble drugs, increased bioavailability, controlled release, and targeted drug delivery.

The core of a micelle is a hydrophobic environment formed by the inward-facing hydrocarbon tails of the amphiphilic molecules. This hydrophobic core attracts and encapsulates non-polar solubilizates.

The outer region of a micelle is a polar environment, formed by the outward-facing polar heads of the amphiphilic molecules. This region interacts favorably with the aqueous environment.

Each particle in a hydrophilic colloid is made from a single molecule. These molecules become highly solvated (surrounded by water molecules) and form stable dispersions.

Lyophobic colloids require specific physical or chemical methods to reduce particle size to the colloidal range. These methods could include grinding, milling, or chemical reduction. Stabilizers like surfactants are needed to keep them dispersed.

Lyophobic colloids are not naturally hydrated by the dispersion medium, such as water, and need stabilizers like surfactants to stay dispersed. This is due to their weak attraction to the surrounding medium.

Intravenous fat emulsions form lyophilic colloids. This means that the fat particles are attracted to the water-based medium, creating a stable dispersion. Stabilizers, like emulsifiers, are crucial for this to occur.

Micelles are spherical aggregates of amphiphilic molecules, like surfactants, that form in aqueous solutions. They have a hydrophobic core and a hydrophilic outer shell. Each micelle contains many monomers.

Micelles and amphiphiles that exist separately in a low concentration at a liquid medium have subcolloidal dimensions. The colloidal range starts at a certain threshold of concentration.

The typical environment in the core of micelles formed in an aqueous dispersion medium is hydrophobic. This means that the core attracts and encapsulates nonpolar substances, like oils or fats.

Liposomes coated with water-soluble polymers to evade rapid removal by the Mononuclear Phagocyte System (MPS), increasing circulation time and drug delivery efficiency in the bloodstream.

The main disadvantage of liposomes is their rapid removal from the bloodstream by cells of the MPS, limiting their circulation time and drug delivery efficiency. This can lead to a decrease in the drug's effectiveness.

Doxil is a stealth liposome that uses pegylation to extend its half-life up to 55 hours. This extended circulation time allows for better drug delivery and efficacy.

The delivery of drugs encapsulated in liposomes is less susceptible to degradation due to their protective encapsulation within the liposome's bilayer.

Nanotechnology is the design, synthesis, and application of materials and devices with dimensions of 1-100 nanometers. Nanoparticles are microscopic particles with at least one dimension in this size range.

The process of bringing water-insoluble or partly soluble substances into an aqueous solution by incorporating them into micelles. Nonpolar solubilizates reside in the micelle's center, while slightly polar solubilizates reside partially or fully within the micelle. Amphiphilic solubilizates, with both hydrophilic and hydrophobic portions, reside partially on the micelle's surface and partially inside.

If the concentration of surfactants is too low, there aren't enough micelles to solubilize the substance, leading to its precipitation out of the solution.

Vitamin A palmitate is the vitamin most likely to be solubilized in Adult Infuvite. This is because it is the most hydrophobic (not like water) component of the vitamin mixture.

In Adult Infuvite, the inactive ingredients, Vitamin K1, alpha-tocopherol acetate, and cholecalciferol, are responsible for solubilization. They act as surfactants, forming micelles to encapsulate the vitamins and keep them dissolved.

Microemulsions offer advantages such as physical stability (don't separate), increased drug solubility, and enhanced drug release due to their small droplet size. They typically consist of two surfactants to lower interfacial tension and are formed spontaneously.

Since they are small, they have a large surface area. Larger surface area means a greater chance of solubilization.

Microemulsions typically use two surfactants to reduce the interfacial tension between the oil and water phases. This allows for the spontaneous formation of small droplets.

The amount of surfactant in microemulsions is relatively large compared to other formulations to achieve stability. This ensures that the small droplets are well-dispersed and don't coalesce.

Multilamellar Vesicles (MLV) are large, with multiple concentric phospholipid bilayers, offering high stability but lower drug encapsulation efficiency. Large Unilamellar Vesicles (LUV) have a single bilayer and offer good encapsulation efficiency for hydrophilic drugs but are less stable.

Small Unilamellar Vesicles (SUV) have a single bilayer and are smaller than LUVs, facilitating tissue penetration and prolonged circulation. However, they can be unstable due to their small size.

Liposomes can accommodate both water-soluble and lipid-soluble drugs. Water-soluble drugs reside in the aqueous core, while lipid-soluble drugs are located within the lipid bilayers.

Factors like the chemical structure of the molecule (hydrophilic vs. hydrophobic), its concentration, and the presence of surfactants and other molecules in the environment determine whether a molecule will form micelles or liposomes.