Disclaimer: This is an example of a student written essay.
Click here for sample essays written by our professional writers.

Any scientific information contained within this essay should not be treated as fact, this content is to be used for educational purposes only and may contain factual inaccuracies or be out of date.

Studying Nanoparticles Formed by Sonication and Extrusion

Paper Type: Free Essay Subject: Sciences
Wordcount: 2168 words Published: 8th Feb 2020

Reference this


Liposomes are established drug carriers for inhalation owning their safety and ability to provide controlled drug release in the lung. These carriers can entrap a wide range of therapeutic molecules for delivery to the peripheral airways using air jet nebulizers.(1)

In air-jet nebulizers, compressed gas is used to convert a liquid into a spray.(2) The jet of high velocity gas is passed through a narrow nozzle and an area of negative pressure, where the air jet emerges, draws liquid from a reservoir up a feed tube. The fine filaments of fluid collapse into droplets as a result of surface tension.

Get Help With Your Essay

If you need assistance with writing your essay, our professional essay writing service is here to help!

Essay Writing Service

In general, aerosols with a size range of 5-10 µm are mainly deposited in the large conducting airways. Particles with a 1-5 µm size range are deposited in the small pulmonary airways. On the other hand, nanosized carrier systems have recently gained increasing attention for pulmonary drug delivery. This is due to their advantages for targeted deposition and reduced dosing frequency to improve patient convenience.(3)

Nanocarriers can be formulated and processed to differ in terms of size. Techniques such as sonication and extrusion are employed to control the size and size distribution of different drug carrier systems. However, the most effective particle size has not been determined yet.

2.     AIM

The aim of the study was to investigate and compare the nanoparticles formed by sonication and extrusion.

For this purpose, liposomes were prepared and analysed before and after each size reduction technique then nebulized via a 2-stage impinge.

3.     Materials and Methods

Liposomes were produced by dissolving a known amount of phospholipid (201 mg) by the addition of ethanol (300 µl) in a glass vial. After the addition of ethanol, the solution in the glass vial was placed in a water bath (70 ºC) for 2 minutes. Once removed from the water bath, 2 mL of water was added to the mixture. The solution was then held on a vortex mixer for 2 whole minutes. A further 17.5 mL of water was added to the mixture to make the total solution to 20 mL. Another run of vortex mixing for 2 minutes before leaving the sample settle for 15 minutes. This allows hydration to take place which forms the liposomes.

Size analysis before size reduction technique using laser diffraction Malvern Spraytec laser diffraction size analyzer was used to determine the size and size distribution of liposomes.

Formulation placed into Qsonica sonicator for 5 minutes at 65 frequency soundwaves. The ethanol-based proliposome formulation was diluted with water at a ratio of 1:10 and pipetted into a cuvette. The cuvette was placed into the Malvern Zetazizer to analyse the size and size distribution.

Another sample of the ethanol proliposme was analyzed before extrution. Once analysed, the vial containing the ethanol-based proliposome formulation was poured into the extrusion machine, which contained a polycarbonate membrane made up of a polycarbonate membrane made up of polycarbonate trach etched filter with a pore size of 400 nm and a Whatman drain disc. The temperature of the machine was 45 ºC and the formulation was passed through the membrane 5-10 times. The particle size was then diluted and measured again.

A two-stage impinge was assembled and set up by filling its lower stage with 30 mL and its upper stage with 7 mL deionised water and by setting the flow rate at 60 L/min. Following pipetting the formulation (3 mL) into the nebulizer reservoir, the mouthpiece of the nebulizer was directed towards the “throat” of the imponger and nebulization was performed, and the time taken was recorded. Nebulisers were weighed whilst empty, after loading with formulation. Aerosol mass output (%) was calculated by measuring the weight difference of the nebulizer before and after nebulization. The aerosol output rate was determined as the mass of liquid nebulized per unit time (mg/min). Samples were collected from the lower impinge, upper impinge and nebulisor reservoir for particle size analysis using the Malvern Zetasizer.

4.     Results

The extrusion machine produced the liposomes with the highest mean mass output (83.9%) closely followed by the probe sonication method (83.8%) (Table. 1). By contrast, the probe sinication device produced liposomes with a higher mean aerosol output rate (174.7 mg/min).

Table 1. Characteristics of liposomes obtained from probe sonication and extrusion size reduction techniques.

Size Reduction Technique

Mean Mass output (%)

Mean Aerosol output Rate (mg/min)

Probe Sonication







Laser diffraction results confirmed that both techniques used were successful in reducing particle size and producing a better size distribution value (Table. 2). From data (Table. 2) it can be deduced that the probe sonication technique produced the smallest particle size. However, the extrusion method achieved a better PDI value compared to the sonication method along with a smaller standard deviation.

Table 2. Results obtained from before and after size reduction technique and nebulization via 2-stage impinge.


Probe Sonication (mean ± SD)

Extrusion (mean ± SD)

Particle Size (nm) Before Size Reduction

1910.75 ± 706.28

2694.75 ± 490.67

PDI Value Before Size Reduction

0.78 ± 0.16

0.80 ± 0.31

Particle Size (nm) After Size Reduction

224.35 ± 42.91

461.08 ± 67.18

PDI Value After Size Reduction

0.47 ± 0.16

0.18 ± 0.09

Particle Size (nm) In Nebulizer Reservoir

290.20 ± 121.48

458.90 ± 77.22

PDI Value In Nebulizer Reservoir

0.375 ± 0.08

0.32 ± 0.05

Particle Size (nm) In Upper Stage

192.20 ± 12.73

297.70 ± 19.52

PDI Value In Upper Stage

0.41 ± 0.11

0.43 ± 0.04

Particle Size (nm) In lower Stage

178.10 ± 61.09

166.60 ± 67.88

PDI Value In Lower Stage

0.31 ± 0.02

0.33 ± 0.14

Laser diffraction analysis of particles from lower stage of 2-stage impinge shows that extrusion method resulted in smaller particle size but had a greater PDI value compared the probe sonication method.

5.     Discussion

Both size reduction techniques provided high mass output values from the nebulizer (Table 1). A slightly greater percentage from the extrusion method (83.9%) compared to the probe sonication method (83.8%). Therefore, both results suggest a good amount of deposition available in the lower stage of nebulization.

The results for the mean aerosol output rate (Table 1) have a clear difference. The longer nebulization time from the extrusion method meant a smaller amount of drug would be delivered per minute compared to the probe sonication method.

The size reduction from before and after each technique was implemented is difficult to compare due to the difference in initial sizes. However, a percentage decrease calculation suggests that the probe sonication (88.26% reduction in particle size) method was more successful in reducing the particle size compared to the extrusion method (82.29% reduction in particle size). This is further supported by the mean PDI values, a lower value from after probe sonication sonication

Find Out How UKEssays.com Can Help You!

Our academic experts are ready and waiting to assist with any writing project you may have. From simple essay plans, through to full dissertations, you can guarantee we have a service perfectly matched to your needs.

View our services

The two-stage impinge is commonly used for in vitro analysis of aerosol deposition and predicting the likelihood of aerosol to travel to the peripheral airways. Aerosols collected in the upper stage of the impinge are regarded as ‘non-respirable’ as they have a diameter larger than 6.4 µm when the flow rate is set at 60 L/min.(4) These larger or heavier liposomes get caught in the upper stage. Even larger particles were found in the nebulizer reservoir due to the fact they are too heavy to be aerosolized. These liposomes aggregate and fuse together.

Figure 1. Presents the nebulizer reservoir, upper and lower stage in a 2-stage impinge.


The heading of a section should be in Arial 9-point bold, all in capitals (Heading 1 Style in this template file). Sections should be numbered. The rest of the text should be in Time New Roman-10.


Headings of subsections should be in Arial 9-point bold with only the initial letters capitalized (Heading 2). (Note: For sub-sections and sub-subsections, a word like the or of is not capitalized unless it is the first word of the heading.)


You can place figures and tables at the top or bottom of the appropriate column or columns, or in the middle of the text on the same page as the relevant text (see Figure 1, Table 1)

A figure or table may extend across both columns, see Figure 2, but if the table or the figure is spreading over both columns, make sure it is at the top or the bottom of the page.

Captions should be numbered (e.g., “Table 1” or “Figure 2”), centered and placed beneath the figure and above table. Please note that the words “Figure” and “Table” should be spelled out.

6.     Conclusion (10%)

It is particularly important that you state clearly what you have done, and explain how your work adds to the current knowledge (i.e., what you have achieved and how it is unique and helpful).

7.       REFERENCES (5%)

1. Elhissi AMA, Taylor KMG. Delivery of liposomes generated from proliposomes using air-jet, ultrasonic, and vibrating-mesh nebulisers. J DRUG DEL SCI TECH. 2005;15(4):261-5.

2. O’CALLAGHAN C, BARRY PW. The science of nebulised drug delivery. Thorax. 1997;52(2):31-44.

3. Rytting E, Nguyen J, Wang X, Kissel T. Biodegradable polymeric nanocarriers for pulmonary drug delivery. Expert Opinion on Drug Delivery. 2008;5(6):629-39.

4. Hallworth GW, Westmoreland DG. The twin imponger: a simple device for assessing the delivery of drugs from metered dose pressurized inhalers. J Pharm Pharmacol. 1987;39:966-72.



Cite This Work

To export a reference to this article please select a referencing stye below:

Reference Copied to Clipboard.
Reference Copied to Clipboard.
Reference Copied to Clipboard.
Reference Copied to Clipboard.
Reference Copied to Clipboard.
Reference Copied to Clipboard.
Reference Copied to Clipboard.

Related Services

View all

DMCA / Removal Request

If you are the original writer of this essay and no longer wish to have your work published on UKEssays.com then please: