Small angle scattering refers to the coherent scattering phenomenon near the origin (000) node of the reciprocal lattice indiffraction. The scattering angle is on the order of 10-2-10-1 rad. The intensity of the diffracted light is the largest in the direction of the incident light, decreases with the increase of the diffraction angle, and becomes 0 at the angle , and the relationship between and the wavelength λ and the average particle diameter d approximately satisfies the following relationship:
Related formulas
ε0 =
ε0 =
Note: θ is the scattering angle (degrees). Small-angle X-ray scattering (SAXS) technology can study various particles in the range of a few nanometers to hundreds of nanometers. Analysis of small-angle scattering patterns can obtain the long-period structure information of matter, or the shape, scale or mass information of submicron particles (or pores). Small angle scattering is an extremely powerful technique or tool for analyzing the spatial correlation of diffuse objects, such as polymer chains and macromolecules in solution.
According to X-ray diffraction (XRD) theory, when the grain size is less than 100 nm, the broadening of the diffraction peak becomes significant as the grain size becomes smaller. Considering the absorption effect of the sample and the influence of the structure on the diffraction line shape, the grain size of the sample can be used Debye-Scherrer formula calculation.
Related formulas
d =
Note: d is the grain size, nm; B is the integral width at half maximum, which needs to be converted into radians during the calculation process, rad; θ is the diffraction angle, (°); λ is the X-ray wavelength, nm.
Raman scattering method
Raman scattering (LRS) can measure the average particle size of nanocrystalline grains, and the average particle size is calculated by the following calculator:
cm^-1
cm^-1
Related formulas
d = 2π
Note:
B is a constant (different elements have different values); Δπ is the anisotropy factor; ω is the Raman peak frequency; d is the average particle size path.
Nano Drug Delivery System Encapsulation Efficiency Calculator
Encapsulation efficiency is an important parameter of nano drug delivery system, which can be calculated by the following calculator:
Related formulas
encapsulation rate =
x 100%
Note: There are generally two methods for the determination of drug encapsulation efficiency in nano drug delivery systems: 1. Determination after separating free drug from nanocarriers; 2. Direct determination without separating free drug from nanocarriers. The first method requires that the packaged drug is stable and no longer leaks during separation. Separation methods include dialysis, gel column chromatography, high-speed centrifugation, centrifugal ultrafiltration and micro-column centrifugation. The second method mainly uses fluorescence quenching and electron spin resonance spectroscopy.
Detection of anti-tumor Effect in Nude Mouse Model
Taking nude mouse xenograft tumor model as an example, this kind of human cancer xenograft model generally dynamically observes the anti-tumor effect of the test substance through the change of tumor diameter. The corresponding evaluation standard often adopts the relative tumor proliferation rate T/C.
before administration
each measurement
before administration
each measurement
Related formulas
V =
ab2
RTV =
T/C =
x 100%
Notes: RTV is the tumor volume; a and b are the length and width of the tumor, respectively; RTV is the relative tumor volume;is the tumor volume measured before administration;is the tumor volume at each measurement;
T/C is the tumor proliferation rate;is the RTV of the treatment group;is the RTV of the negative control group.
In principle, evaluation criteria: T/C>40% is invalid;
T/C≤40%, and after statistical processing P<0.05 is effective.
Among all human cancer xenograft tumor models used in the in vivo efficacy test,
generally at least three should meet the effective standard before it is suggested that the test substance needs to enter clinical trials.
Encapsulation efficiency (ee) is an important indicator to measure liposome quality, and it refers to the ratio of encapsulated drug to the total amount of drug in liposome suspension. The key to determining the encapsulation efficiency is to separate the unencapsulated free drug from the liposome suspension without destroying the liposomes. Commonly used separation methods include gel column permeation chromatography, dialysis, ultracentrifugation, ultrafiltration membrane filtration, and protamine aggregation.
Gel column permeation chromatography is more commonly used and is suitable for the determination of the encapsulation efficiency of water-soluble drugs that do not adsorb to gel particles, but this method is not suitable for fat-soluble drugs. Free fat-soluble drugs cannot be eluted from the gel column by aqueous media, so the method cannot be validated. Because many sites on the surface of dextran can bind and interact with the liposome membrane, some lipids will be lost, leading to changes in membrane permeability and leakage of packaged substances, making the determination of encapsulation efficiency inaccurate. This phenomenon can be solved by pre-saturating the column with blank liposomes or increasing the amounts of liposomes on the column. Generally, small single-chamber liposomes made of 20 mg of lipids can saturate 10 g of gel.
Encapsulation Efficiency Calculator for Gel Column Permeation Chromatography:
The type of quantity
Liposome collection solution
(mM)
(mL)
Total drug in the liposome suspension
(mM)
(mL)
Related formulas
ee =
x 100%
Note: cL is the drug concentration in the liposome collection solution; VL is the volume of the collection solution per tube; cT is the total drug concentration in the liposome suspension; VT is the volume of the sample solution.
Dialysis Method
The small holes on the dialysis bag can intercept large molecules and allow small molecules to pass through, which can effectively separate drug molecules (except macromolecular drugs) and liposomes. The molecular weight cut-off is for linear molecules such as proteins. For drug molecules with generally small molecular weights, the molecule has a large space volume, so it is necessary to choose a dialysis bag with a large molecular weight cut-off. Usually, the recovery rate of free drug is selected as an index to ensure that drug molecules can pass through the dialysis bag smoothly, and liposomes do not leak. The dialysate medium needs to have high drug solubility and cannot destroy the liposome structure. Encapsulation ratio calculator for this method:
(mg/mL)
(mg/mL)
(mL)
(mL)
Related formulas
ee =
x 100%
Note: CB is the equilibrium concentration of the drug in the dialysate at dialysis equilibrium; VB is the volume of the dialysate; cT is the total drug concentration in the liposome suspension without dialysis; VT is the volume of the liquid in the dialysis bag.
Protamine Aggregation Method
Protamine is rich in basic amino acids, with an isoelectric point of 10-12, soluble in water and dilute acid, and has good thermal stability. Due to its positive charge, polycationic protamine will flocculate with negatively charged or neutral liposomes, and routine centrifugation can separate liposomes from free drug. Therefore, it is a coagulation centrifugation method aimed at the charge properties of liposomes or nanoparticles, and has the advantages of rapidity and strong operability.
The Encapsulation Efficiency Calculator for this method is:
(mg/mL)
(mg/mL)
(mL)
(mL)
Related formulas
ee =
x 100%
Note: CB is the free drug concentration in the supernatant; VB is the centrifuge volume (5. 2mL); cT is the total drug concentration in the original liposome suspension without protamine aggregation; VT is the sample volume (0. 1 mL).
Liposome Drug Loading Calculator:
Related formulas
Drug loading =
x 100%
Phospholipid Oxidation Index Calculator
For the absorbance at 233nm and 215nm, use the following formula to calculate the oxidation index, and the oxidation index should be controlled below 0.2.
Related formulas
Oxidation index =
If the drug or other excipients in the sample absorb at 233nm or 215nm, it will affect the determination and evaluation of the oxidation index. At this time, the oxidation-reduction titration method can be used to determine the peroxide value of the sample. The principle is that phospholipids are oxidized to produce peroxides with a diene structure, which can quantitatively oxidize iodide ions in potassium iodide into free iodine, which can be titrated with sodium thiosulfate. The peroxide value is expressed in terms of the amount of iodine that frees potassium iodide per liter of sample (in millimoles), called peroxide value (POV). The general standard is tentatively set at no more than 15meq/L.
The peroxide value is calculated in W3, and the value is expressed in milliequivalents of active oxygen per kilogram (meq/kg), and the calculator is as follows:
(mL)
(mL)
(N)
(g)
Related formulas
W3 =
Note: V is the numerical value of the volume of sodium thiosulfate standard titration solution consumed by the titration sample, in milliliters (mL); V0 is the numerical value of sodium thiosulfate standard titration solution volume consumed by titration blank, and unit is milliliter (mL); c is the accurate numerical value of sodium thiosulfate standard titration solution concentration, and unit is mole per liter (mol/L); m3 is the numerical value of sample quality, the unit is gram (g)1000 is the conversion factor.
Liposome leakage rate Calculator
Liposome leakage rate There are generally three types of drugs in liposomes, namely adsorption, encapsulation and embedding. Drugs, liposomes, and surrounding solutions are in a state of equilibrium. Drugs in liposome suspension are affected by factors such as solution concentration gradient or plasma protein binding, resulting in drug leakage. Therefore, it is necessary to detect the stability of liposomes in PBS solution or plasma protein solution in vitro, that is, the leakage rate. During actual operation, the liposome preparation is usually diluted 10 times with PBS buffer or plasma protein solution, and the measurement method is the same as the encapsulation efficiency measurement, and is evaluated with the leakage rate curve (the ordinate is the leakage rate, and the abscissa is the time).
The leak rate calculator is:
Related formulas
percolation rate =
x 100%
percolation rate =
encapsulation rate (Before storage) - encapsulation rate(store for a certain period of time)
