Fast-Tracking Nanomedicine Development with Tunable Resistive Pulse Sensing

By AZoNano Staff Writers

Topics Covered

Introduction
Requirements for Efficient Development of Nanomedicines
Tunable Resistive Pulse Sensing - Meeting Nanomedicine Analysis Needs
TRPS Provides Assurance Through Calibration
Accurate and Direct Measurement of Particle Concentration with TRPS
Determination of Drug Delivery Particle Dosage with TRPS
TRPS Size Analysis for Optimizing Liposome Synthesis
TRPS Size Analysis for Monitoring Nanomedicine Stability
Particle-by-Particle Size and Charge Analysis
Conclusions
About Izon

Introduction

To develop complex nanomedicines, it is essential that physical characterization data is available for the transition from the laboratory to the market. The manufacture of nanomedicines requires the assurance that the physical properties of nanomedicines will be equal to those of off-patent drugs, ensuring efficacy and safety of these treatments.

Since the concentration, size and surface charge of nanomedicines directly impacts their in vivo efficacy and safety, there is a need for a precise and sensitive analysis technique that measures the properties of each particle in physiological conditions, as shown in Figure 1.

This article describes how tunable resistive pulse sensing (TRPS) can offer a more predictable development pathway for moving nanomedicines out of the lab, and into the clinic.

Figure 1. Importance of the physiochemical properties of drug delivery particles

Figure 2. A tri-modal particle dispersion with peaks at 200nm, 280nm and 350 cannot be resolved by DLS (red curve), but is easily resolved by TRPS (blue). Precise particle concentration (particles/mL) can be obtained with TRPS (y-axis), but not with DLS, which is expressed in intensity-weighted distribution.

Requirements for Efficient Development of Nanomedicines

Effective development of nanomedicines must offer the following:

  • Offer an accurate, precise and repeatable suite of particle measurements
  • Provide "particle fingerprinting" with agreed suite of relevant measurements
  • Replace the present method of tight control of GMP process, which is not practical in scale up situations
  • Be practical and cost effective

The important physical properties of nanomedicines are:

  • Accurate particle size distribution
  • Precise measure of particle aggregation
  • Particle concentration
  • Characterization of particle surface charge (zeta-potential)
  • Particle interactions, including formulation stability (aggregation) and biomole-cule interaction
  • Particle interactions, including aggregation and biomolecule interaction

Tunable Resistive Pulse Sensing - Meeting Nanomedicine Analysis Needs

Tunable Resistive Pulse Sensing (TRPS) using Izon's qNano nanopore-based system is a particle-by-particle high resolution technique commercially available for accurate determination of the size (Vogel et al. 2011), concentration (Roberts et al. 2012) and charge (Kozak et al. 2012) of 50nm-10µm structures.

The measurement of individual particles from the resistive pulse they generate as they traverse a tunable pore as shown in Figure 3. TRPS has been shown to offer the detailed measurement required to offer representative information on polydisperse samples, not possible with ensemble bulk-analysis techniques for submicron particle sizing (Anderson et al. 2013).

Figure 3. Particle by Particle measurement with TRPS. When a particle enters the pore it blocks a proportion of the ions flowing through the pore - this causes a pulse in the ionic current the magnitude and duration of the pulse is proportional to the particle size and velocity, respectively.

TRPS Provides Assurance Through Calibration

A main advantage of TRPS measurement is that it offers assurance of accuracy through calibration using reference standards, which have been validated against NIST-traceable standards. These particles behave as a reference point against which very accurate and precise measurements of an unknown sample can be made as shown in Figure 4.

Figure 4. Samples can be accurately measured in comparison to standards of known size and concentration.

Accurate and Direct Measurement of Particle Concentration with TRPS

Direct measurement of particle concentration is enabled with TRPS. The concentration in particles/mL is directly proportional to the particle count rate (particles/min), which is independent of the particle size or polydispersity.

This is shown by the linear decrease in particle rate for a serial dilution (1:10, 1:25 -1:100) of the liposome sample. Figure 5 shows the measured count rates and corresponding concentration values, which are the average and standard deviation of three analysis runs for the liposome sample.

Figure 5. Particle rate is directly proportional to sample concentration. Reference: Roberts et al. (2012) Biosensors and Bioelectronics 31 pp. 17-25

Determination of Drug Delivery Particle Dosage with TRPS

It is possible to calculate the deliverable nanomedicine particle volume fraction dosage by measuring the properties of each particle and their concentration. The example shows how the exact volume fraction of deliverable drug is calculated for a liposomal sample as shown in Figure 6.

Figure 6. Measuring the Impact of nano-scale drug delivery. TRPS provides the ability to measure equivalent amount of drug delivered by different sized particles (A), this allows the size-specific volume fraction to be calculated (B).

TRPS Size Analysis for Optimizing Liposome Synthesis

High resolution measurement enables precision and confidence in tailoring the size of liposomes in solution. Figure 7 shows how extrusion through a 100 and 200nm filter affects liposomal size distribution.

Figure 7. High resolution analysis for optimizing liposome production with 100nm (blue) vs 200nm (red) filter extrusion.

TRPS Size Analysis for Monitoring Nanomedicine Stability

High resolution analysis with TRPS offers confidence in understanding the impact of treatment and storage conditions of long-term stability of nanomedicine solutions. The size and concentration of a liposome formation was analyzed showing an increase in sample dispersity after freeze-thaw treatment.

Particle-by-Particle Size and Charge Analysis

The circulation lifetime of drug delivery particles are improved by modifying the surface such as PEGylation and their specific cellular targeting such as antibodies. These surface features cause a change in the liposome size and charge.

High resolution particle-by-particle Size & Charge Analysis is uniquely available with TRPS, and represents a new way to characterize and understand particles. It is possible to evaluate PEGylation in detail with TRPS while replacing a phosphocholine lipid with a glycolated phospholipid gives rise to a negative charge.

The corresponding negative shift and distribution in particle zeta-potential helps monitor the degree of liposome PEGylation.

Conclusions

In order to offer more reliable data for accelerated development of pre-clinical nanomedicines. Tunable Resistive Pulse Sensing is a high resolution technique capable of providing assurance of the physical properties of nanomedicines formulations.

About Izon

Izon Science has developed the world’s first nanopore based measurement system available for general use. Izon’s instruments are used for precise measurement and analysis of individual particles across a wide range of scientific fields including bionanotechnology, nanomedicine, vaccinology, microbiology, biomedical research, environmental science, and particle based nanoscience. Izon originated in New Zealand and now sells its products in 34 countries. It has its European headquarters in Oxford, UK and its US headquarters are in Cambridge, MA.

This information has been sourced, reviewed and adapted from materials provided by Izon.

For more information on this source, please visit Izon.

Date Added: Feb 20, 2014 | Updated: Feb 24, 2014
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