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COLLOIDAL SOLUTIONS 1 Solutions vs Colloids The solution - this is a mixture of one or more substances which are dispersed in solvent (e.g. water). The true solution is a one phase system because it has dispersed particles below 1nm: • particles can not be detected by optical means, like microscopes, including an ultra microscope. • solution is homogeneous, as one-phase liquid (e.g. one solvent or pure water). • does not show the Brownian movement. • may pass throug dialitic membrane 10-9 m = 1 nm = 0.001 micron 10-7 m = 100 nm = 0.1micron 10-6 m = 1000 nm = 1 micron (Hair diameter 17 to 180 microns ) 2 Solutions vs Colloids Solutions: • • • Transparent to ordinary light Stable unless solvent evaporated May pass through dialytic, but not true osmotic, membranes 10-9 m = 1 nm = 0.001 micron Colloids: • • • • 10-7 m = 100 nm = 0.1 micron 10-6 m = 1000 nm = 1 micron Typically 1-100 nm or more per particle Not totally transparent – Tyndall Effect May separate out Particles are to large to pass through most membranes 3 COLLOIDAL SOLUTIONS COLLOIDAL SOLUTION – HETEROGENEOUS system with particle size of 10-9-10-7 m in diameter (1 – 100 nm, up to 500 nm) 10-9 m = 1 nm = 0.001 micron 10-7 m = 100 nm = 0.1 micron 10-6 m = 1000 nm = 1 micron 4 The colloidal system [synonyms: colloidal state, colloid, sol or colloid ] solution – are heterogeneous dispersive (mostly two phase ) configuration, in which we can distinguish two phases: • continues - dispersing phase - solvent(s) or bulk material which is relatively very small in size particles (e.g. water particles are about 0.1 by 0.2 nm) • not continues - dispersed phase which particles diameter are relatively large, 1-100 nm (10-9 – 10–7 m), and in case of biopolymers – up to 500 nm. 5 Properties of colloids: 1. They can be seen in ultra–microscope. Attention: the difference between an ultra-microscope and ordinary one is that in the former the light falls laterally on the liquid under study, instead of “from below”. The ordinary microscope with x400 magnifications has limitations for particles below 1 micron, but it is still able to show “general structures of colloid system”. 2. They are not dialyzed –> Colloidal particles will not be separated by membranes (like bladder or parchment paper), because they will not diffuse through a membrane. 3. They show permanent Brownian motions – mostly particles smaller than 100nm are able to make strong Brownian motion. 4. They show Tyndall effect – visible scattering light by the colloidal particles. 5. They may coagulate –> colloid particles become agglomerated. 6 Types of solutions depending on size of disspersed phase in dispersive medium TYPE OF SOLUTION DIAMETER OF PARTICLES OF DISPERSED PHASE True solution (homogeneous) < 10-9 m (<1nm) Colloidal (heterogeneous) 10-9 - 10-7 m (1-100 nm) Suspension > 10-7 m (>100 nm) 7 •Colloidal systems are wide spread in nature in organic or inorganic form. •All cells in human body are some kind of colloidal system with different concentration (proteins, peptides, hydrocarbons, skin,hair) 8 Tyndall Effect This is light scattering by colloidal example by dust, fog, milk,etc.). solution (for When light beam passes through the colloidal dispersion it is scatter and therefore is visible. When light beam passes through the solution, like water, does not scatter and therefore it can not be seen. Intensity of this phenomena is larger when difference between light scattering of dispersive medium is larger then light scattering of dispersed phase. © 9 Solutions vs Colloids The Tyndall Effect True Solution e.g. water Colloidal mixture, e.g. milk © 10 The Tyndall Effect © 11 CLASSIFICATION OF COLLOIDAL SYSTEMS DEPENDING ON : I. STATE OF DISPERSSING AND DISPERSSED PHASE Disperssed phase Disperssing phase COLLOID EXAMPLE Gas Liquid Solid Gas Gas Gas Aerosol liquid Aerosol solid Fog, clouds, vapors Smoke, dust Gas Liquid Liquid Liquid Foam Emulsion Solid Liquid Zol Foam: soap, beer Creams, nail polish, milk, mayonese, butter Polymer solutions Gas Liquid Solid Solid Solid Solid Foam Emulsion solid Zol solid Pumice, styrofoam Gels, opal Glass rubin, colour cristals © 12 The most common and important colloidal system are solutions of liquid in liquid and solid in liquid – called respectively emulsions and sol. There are following examples of emulsions: • Water in oil such as cream, butter - they do not conduct electrical current. • Oil in water such as milk (colloid of protein and fat in water) – they conduct electrical current. Colloids depending on temperature and concentration can exist in liquid form as a sol, or as a elastic solid - called gel. • Soles are often transparent and look like true solution. Dispersed particles are separated from each other by dispersive phase. • In gels dispersed particles are connected with each other and create spherical structures in which some of the area is filled with solvent. This structure gives characteristic “jelly” constituency. 13 CLASSIFICATION OF COLLOIDAL SYSTEM DEPENDS ON: II. Size of colloidal particles: monodispersive (particles of dispersed phase have the same dimensions) polidyspersive (particles of dispersed phase have the different dimensions) III. Ratio of dispersed phase to dispersing medium : liophilic colloids – they have large affinity to solvent particules; colloidal particles are serrunded by solvents particles liophobic colloids – they have small affinity to solvent and absorb on the particles surface large quantities of one type of ions © 14 CLASSIFICATION OF COLLOIDAL SYSTEM DEPENDS ON (cont.) IV. Quality of dispersive phase: Emulsions – the dispersed phase solutions of nonpolar substances (e.g. lipids) which do not have affinity with dispersing phase (e.g. water). Emulsions have hydrophobic character and are also called suspenssions or not-reverse colloids. • In living organisms example of emulssions are lipids. Small particles of lipids can be dispersed in water thanks to the compounds called emulsifiers. Emulsifier – this is compund which can be „dissolved” in both dispersed and dispersing phase. For example consumed fats are emulsified by bile acids included in bile. They have ability to decrease surface tension, like soap in water. 15 DIFFUSION COATING AgI micell structure precipitated with excess of KI Nuclei of colloidal molecule +adsorbing layer core micell 16 COLLOIDS STRUCTURE Hydrophobic micell are mostly built by oxides, sulphates, hydroxides of heavy metals Hydrophilic colloids are built usually from large molecules such as : proteins. Their stability are due to the presence of water molecules adsorbed on their surface. 17 Coagulation (1) COAGULATION – it is ability of colloid particles to combine with each other and form larger structures called agregates. After reaching appropriate size they loose ability „to flow” and they sediment on the bottom. Coagulation can be caused by: 1. 2. 3. 4. 5. radioactivity– beta ray heating – coagulation of protein (egg) evaporation or freezing of dispersive medium dehydration, for example by using acetone, alcohol addition of electrolite to colloid © 18 Coagulation (2) Peptization – process reverse to coagulation – breaking coagulate and return from coagulate to colloid. SOL coagulation GEL peptization 19 Coagulation (3) Hydrophilic colloid (reversible) – takes place when water coat has been removed Hydrophobic colloids (irreversible) – takes palce when electrical charge present on the surface become neutralized. 20 HYDROPHOBIC COLLOIDS HYDROPHILIC Salts with multivalance cations coagulate Water particles 21 Coagulation (4) Conditions for salting out of protein • Proteins are easiest to be salt out in isoelectric point (pI) because they do not posses any electrical charge, they attract themselves the most and they are aggregate which leads to precipitation. ( no electrical charge helps molecules to join in aggregates which allows to precipitate from solution). • In pH different from pI, protein due to charge presence can exists in solution despite not having water coat ( they behave similar as hydrophobic colloids) • Addition of small amount of neutralizing electrical charge ions leads to protein precipitation. Such as protein do not posses neither electrical charge or water coat. 22 Conditions for salting out protein from solution Protein ion Protein cation Protein in pI Acid addition pH increase pH decrease dyhadration dyhadration dyhadration Base addition charge lost due to anion addition Charge lost due to cation addition precipitate Protein anion Protein cation suspenoid © 23 Salt-out of proteins • Proteins are easy to salt-out in isoelectric point (pI) and in this state they easily sediment as a larger aggregates. [Isoelctric point it is pH at which proteins are amphoteric and have no electrical charge]. • In pH different than pI protein can exist in solution despite having no hydrophilic coat. 24 Preparation methods of colloidal systems (1) Colloids preparation liophilic Dissolving liophobic Dispersion methods Condensation methods © 25 Preparation methods of colloidal systems (2) Dispersion methods Size reduction until obtaining colloids by: mechanical means (colloidal mill) electrical means – to obtain sole of metals, metal oxides, etc. ultrasounds (20000Hz) to obtain e.g. dyes, gypsum. In this group is also peptization. This tools are separating combined colloidal molecules. © 26 Preparation methods of colloidal systems (3) Condensation methods Colloid’s size reduction is obtain by addition of particular chemical molecules. There are following methods to obtain it: polymerization decreasing in solubility (e.g.: receiving of colloidal solution of sulphur in water by pouring saturated solution if sulphur in alcohol into water) reduction (e.g. nobel metal ions) oxidation ion exchange (e.g.: AgNO3 + KI AgI + KNO3) hydrolysis (e.g.: metal hydroxyls) © 27 PROTECTIVE ROLE OF HYDRPHILIC COLLOIDS ON HYDROPHOBIC COLLOIDS Hydrophilic colloids show higher stability than hydrophobic colloids, because of two stabilizing factors: hydration layer sometimes particles have the same charge (which can be result of dissotiation of acidic or basic groups being present in colloidal particle) Hydrophilic colloids are acting protective on hydrophobic colloids – addition of hydrophilic colloid to hydrophobic is causing creation of stable system from which it is difficult to precipitae suspended particles (e.g. small amount of protein added to colloidal gold suspension are protecting it from coagulation). Protective role of colliod can be determined quantitatively by providing gold number ( gold number it is the smallest amount of miligrams of protective colloid in respect to pure substance which is able to protect 10cm3 0,1% of formaldehyde gold zol, against color change from red to purple after addition 1cm3 10% NaCl ) 28 Colloids in fluid therapy (1) Fluid therapy (1): treatment consisting of fluid intake (usually intravenous, intraarterial or subcutaneous) often used to treat both hospital and emergency 29 Colloids in fluid therapy (2) Fluid therapy (2): leveling fluid deficiency is one of the most urgent tasks in the treatment of critically ill patients with hypovolemia hypovolemia -a decrease in intravascular volume, resulting in insufficient functioning of the normal mechanisms to hold fluid in the bearing - may exists as a reduced, normal or increased extracellular volume - large hypovolemia is leading to hypovolemic shock Keeping adequate fluid therapy contributes to the reduction of organ disfunction and shortens hospitalization. 30 Colloids in fluid therapy (3) Basic conditions requiring fluid therapy : all forms of shock (usually hypovolemic shock, but also anaphylactic shock, septic, neurogenic) dehydration due to increased fluid loss (diarrhea, vomiting) burns (increase in vascular permeability in the case of burns results in the loss of fluid to the patient) deficiency states of other body fluids 31 Colloids in fluid therapy (4) The objectives of conducting fluid therapy : replenishment of electrolytes and nutrients replenishing fluids (eg. blood lost as a result of hemorrhage) supply of drugs in combination with liquid (when the medication should be administered for several minutes or at high dilution) 32 Colloids in fluid therapy (5) Fluids used for fluid therapy : Crystalloids (aqueous solutions of electrolytes or glucose, such as 0.9% NaCl, 5% glucose solution, Ringer's solution, polyelectrolitic isotonic fluid "PWE") - used for blood loss up to 15% of body weight indicated in patients who have a deficiency of fluid in the interstitial space or patients with immunodeficiency electrolyte (burned and dehydrated) - Colloidal solutions (natural and synthetic ) - used for blood loss exceeding 15% of body weight - indicated in situations where there is insufficient supply of crystalloid or are contraindication for their use (eg. risk of pulmonary edema) -it is estimated that administration of 1 liter of colloidal solution corresponds to the administration of 4 liters of crystalloid 33 Colloids in fluid therapy (5) cont. Blood and blood-related products : - packed red cells, (RBC, pRBC, PRBC), - fresh frozen plasma (FFP), - blood plates concentrate http://reference.medscape.com/drug/ffp-octaplas-fresh-frozen-plasma-999499 34 Colloids in fluid therapy (6) Colloidal solutions synthetic natural gelatines - made of collagen obtained of tendons, skin and bones - Small molecular weight - 35 kDa (fast urinary excretion ) - short-term volume effect Human albumin - works for 24–36 h, - reraly cuases allergic reaction - big quantities may cause coagulopathy - used in: severe protein deficiency states , extensive burns, brain edema ascites expensive - A minimal effect on hemostasis starch hydroxyl (HAES/HES) -Synthethised from amylopectine -- HES: Plasmasteril (6% HES 450/0.7) and 3%, 6%, 10% solutions HES:, HES 200/0.5, HES 200/0.5, HES 130/0.4 - prefered: show beneficial rheological effect and inhibition of blood plates aggregation does not accumulate in plasma and tissues and does not affect hemostasis and renal function dextran - polymers consisting of 200-450 glucose molecules - have been used in the clinic : 6% i 10% dextran solution 40 (T1/2= 2-3 h) 6% dextran solution 70 (T1/2= 6-8h) - used to supplement intracellular volume by improving reological properties of blood, in anticoagulant therapy - Amoung colloids are the most often causing anaphylactic reactions 35 Colloids in fluid therapy (7) Colloidal solutions - advantages : allow for faster replenishment of intravascular space (hemorrhage, shock) compared to crystalloids provide faster, stronger and longer-lasting volume effect - are causing oncotic pressure increase, which leads to the movement of water into the vessel - remain - long in the intravascular compartment (2-12 hours) after administration of colloids an increase in intravascular volume is observed – from 100 % to up to 400% have a positive impact on hemodynamics, organ perfusion and oxygen supply 36 Colloids in fluid therapy (8) Colloidal solutions -disadvantages : can cause allergic reactions after the administration of large amounts may occur : - dilution effect of blood components: proteins, coagulation factors - decreases in hematocrit concentration price 37 Colloids in fluid therapy (9) Ideal colloidal solution: should not accumulate in the plasma and tissues, but readily undergo elimination from the body HES 130/0,4 should not affect hemostasis and renal function should be suspended in crystaloid solution to avoid dehydration of extracellular space and impairment of kidney functions 38 The End 39