Silica vs. PS NP etching rates

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Qualitative Analysis: SiO2 and Polystyrene

NP Etching Using Lactic Acid

Ann Meek | Sarin Parikh |Suranjan Oruganti

Shout Out

Dr. Esener,

Negin M., Yasan Y., and Mukanth V.

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OutlineI. IntroductionII. Objective and BackgroundIII. ProcedureIV. ResultsV. DiscussionVI. Conclusion

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Motivation

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“Convincing the macrophages that the nanoparticles were part of the body and shouldn’t be cleared.”

To the left: A peptide “passport” attached to nanoparticles tells macrophages “Don’t eat me” (credit:: Mary Leonard, Biomedical Art & Design)

Introduction

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To engineer quasi-molecular complexes for

highly specialized delivery, it is essential to understand

endocytosis (right): the mechanism by which a cell internalizes a vesicle from

its’ surroundings.

Melis Çağdaş, Ali Demir Sezer and Seyda Bucak (2014). Liposomes as Potential Drug Carrier Systems for Drug Delivery, Application of Nanotechnology in Drug Delivery, PhD.

Ali Demir Sezer (Ed.),

Objective

The goal of this experiment is to qualitatively assess the etching characteristics of a nanoparticle in an endosomal

environment.

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Why Silica & Lactic Acid?• The material must be versatile in its surface functionality, size-

modulation and porosity. Biological-relevant functionality include: favoring colloidal stability, long-time blood circulation. The evaluation of silica-based nanoparticles as drug carriers has become very popular among the last 5 years or so (Slowing et al. 2008; Di Pasqua et al. 2008; Rosenholm et al. 2010).

• Late endosomes contain lactic acid of pH 4.5-5.5 and could melt away the thin silica shell.

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Effects of nanoparticles on the body

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Flow-chart to the left: Klara Slezakova, Simone Morais and Maria do Carmo Pereira (2013). Atmospheric Nanoparticles and Their Impacts on Public Health, Current Topics in Public Health, Dr. Alfonso Rodriguez-Morales (Ed.),

Procedure

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Procedure

I. Coating with TMOS and APTMSII. WashingIII. CalcinatingIV. Sealing with PLLV. EtchingVI. Analyzing

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I. Coating with TMOS and APTMS

• Polystyrene beads were mixed with 2 samples of ethanol, APTMS and TMOS were mixed in a solution with the beads and sonicated.

11Jung, Hak-Sung, Doo-Sik Moon, and Jin-Kyu Lee. "Quantitative Analysis and Efficient Surface Modification of Silica Nanoparticles." Journal of Nanomaterials 2012 (2012): 1-8. Web.

TMOS

II. Wash• The samples were washed using ethanol • Centrifuged at 4000 RPM, 20 °C for 10 min• Extra liquid was pipetted out

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III. Calcinate• Sample particles mixed with ethanol

and sonicated• Placed on 4 glass slides for 12 hours

at 480 °C• Slide washed once with ethanol and

3x with water and emptied into respective vials

• 3 solutions created with lactic acid at pH 2.1, 4.5, 6.9.

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Void

Polystyrene

Calcinated

Non-Calcinated

Before & After Calcination

Réfega, Ricardo. "Nanoparticles in Biomedical Imaging." Fundamental Biomedical Technologies (2008): Web.14

IV. Seal with PLL

• Silicic acid added to PLL to seal particles overnight.

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Void

Polystyrene

Calcinated

Non-Calcinated

SEM of Nanoparticles

Calcinated Non-Calcinated

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V. Etching• 26 solutions were created using a lactic acid

solution and 37°C bath

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VI. Analysis Each sample placed on siliconwafer for analysis under SEM.

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ResultsDLS

SEM

IMAGE J

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DLS DataNon-calcinated Calcinated

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Results Calcinated at pH 4.5

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10 min 1 hr

6 hr Overnight

Results Non-Calcinated at pH 4.5

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10 min

6 hr Overnight

1 hr

Results Calcinated at pH 2.1

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1 hr

Overnight

Results Non-Calcinated at pH 2.1

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1 hr

Overnight

Results Calcinated at pH 6.9

26overnight

1 hr

Results Non-Calcinated at pH 6.9

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1 hr

Overnight

To Summarize

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Discussion

● PLL protected the silica!● From our results, we gathered that the PLL barrier prevented

the silica from etching.

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Room For Improvment

- Washing: the etching is pH sensitive. - Use Dye as maker: For noncalcinated particles we can use

fluorescent dye in the NP that are released upon rupture. Then use UV-Vis.

- Preventing colloidal aggregation

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Sources of Error

- TMOS and APTMS added in separate vials- Image J was used for analysis

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Conclusion and Thoughts ● It must be noted that agglomerate forms of nanoparticles

might interact differently in a system than in single form.● To keep the nanoparticles in monodispersed suspension,

coatings must be applied● PLL can be used as a protector from etchants● Longer circulating pattern for NP coated with PLL and PEG

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Thank You- Dr. Esener, - (Dr. Tao, Dr. Sirbuly, Dr. Luo, Dr. Horvath).- Negin M., Yasan Y., and Mukanth V.- Thank you audience for listening

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Questions?

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