Optimizing Pharmaceutical 

Formulations

Rahil Verma

Intern for Dr. Rachel Ford

Biomedical Engineering/CS Student at Duke University

SURF Colloquium, August 1–3 2023
Background • Protein drug formulations include 

active protein, preservatives, and 

surfactants among other excipients

• Surfactants used to keep protein dispersed 

evenly in solution

• Preservatives used to prevent 

microbial growth

• Ideally maximize antimicrobial strength 

while remaining evenly dispersed in 

solution

Poloxamer 188

8780 g/mol

x = z ≈ 80; y ≈ 30

2
Background • Protein drug formulations include 

active protein, preservatives, and 

surfactants among other excipients

• Surfactants used to keep protein dispersed 

evenly in solution

• Preservatives used to prevent 

microbial growth

• Ideally maximize antimicrobial strength 

while remaining evenly dispersed in 

solution

Poloxamer 188

8780 g/mol

x = z ≈ 80; y ≈ 30

3
Problem

• Surfactants used to stabilize protein

• Surfactants and preservatives 

are aggregating below solubility limits

- Phenol solubility is 84 mg/mL

- Poloxamer 188 solubility is > 400 mg/mL

• Aggregation → less stable →

degrade function, trigger immune 

response

Phenol

4

Benzyl alcohol Poloxamer 188

Phenol concentration

Turbidity boundary @ 7 mg/mL phenol 
Goal

5

Phenol Benzyl alcohol Poloxamer 188

Turbidity boundary @ 7 mg/mL phenol 

Phenol concentration

• Create phase diagrams at varying 

conditions (Clear/Turbid)

- Turbidity boundary is the first sample 

in phenol spectrum to exhibit turbidity

• Investigate impact of surfactants, 

preservatives, and temperature on 

stability of formulation

• Provide pharmaceutical industry 

with range of stable concentrations
Effect of Benzyl Alcohol

• Used as preservative

• Combined w/ phenol = more 

effective antimicrobial while 

below dose limits

• Decreases turbidity boundary 

by 0.28 mg/mL phenol per 1 

mg/mL increment of benzyl 

alcohol

4

6

8

10

12

14

16

18

0 5 10 15

Turbidity Boundary 

(mg/mL Phenol)

Benzyl Alcohol (mg/mL)

0.1

2.5

5

10

20

P188 

(mg/mL)

37 °C

6

Benzyl alcohol Poloxamer 188
Effect of Poloxamer 188

• Commonly used as a surfactant

- Consistency in production

- Not susceptible to hydrolysis

• Increases turbidity boundary by 

0.26 mg/mL phenol per 1 mg/mL 

increment of P188

7

Benzyl alcohol Poloxamer 188

4

6

8

10

12

14

16

18

0 5 10 15 20

Turbidity Boundary 

(mg/mL Phenol)

Poloxamer 188 (mg/mL)

0

5

9

14

BzOH

(mg/mL)

37 °C
Effect of Poloxamer 188

8

Benzyl alcohol Poloxamer 188

• Commonly used as a surfactant

- Consistency in production

- Not susceptible to hydrolysis

• Increases turbidity boundary by 

0.26 mg/mL phenol per 1 mg/mL 

increment of P188

• Drug formulations typically use 

0.2–0.6 mg/mL P188

4

6

8

10

12

14

16

18

0 5 10 15 20

Turbidity Boundary 

(mg/mL Phenol)

Poloxamer 188 (mg/mL)

0

5

9

14

BzOH

(mg/mL)

37 °C
Effect of Poloxamer 188

• Below 0.05 mg/mL P188 

opposite effect occurs

- In absence of poloxamer 188 

turbidity boundary ~80 mg/mL 

phenol

- But poloxamer 188 increases 

turbidity boundary

*Not a fitted curve

6

6.5

7

7.5

8

8.5

9

9.5

10

0 0.1 0.2 0.3 0.4 0.5

Turbidity Boundary (mg/mL 

Phenol)

Poloxamer 188 (mg/mL)

9 mg/mL BzOH

30 °C

9

Benzyl alcohol Poloxamer 188
Effect of Temperature

• Heating hydrophobic molecules 

like phenol and benzyl alcohol 

helps dissolve in water

• Poloxamer 188 has opposite 

relationship, T ↑ solubility ↓

• Which effect is most prominent?

10

Benzyl alcohol Poloxamer 188

Poloxamer 188 micelle

Temperature
Effect of Temperature • Heating hydrophobic molecules 

like phenol and benzyl alcohol 

helps dissociation in water

• Poloxamer 188 has opposite 

relationship, T↑ solubility↓

• Which effect is most prominent? • Temperature decreases turbidity 

boundary

11

Benzyl alcohol Poloxamer 188

68

10

12

14

16

18

0 20 40 60

Turbidity Boundary (mg/mL Phenol)

Temperature (°C)

0.1

2.5 5

10

20

P188 

(mg/mL)

0 mg/mL BzOH
Effect of Temperature

• Two regimes of turbidity

• 37 °C is critical micelle temperature 

for poloxamer 188

• Hypothesized mechanism for 

aggregation:

- Poloxamer 188 T ↑ solubility ↓

- Phenol prefers polypropylene oxide 

block over water

12

Benzyl alcohol Poloxamer 188

6

8

10

12

14

16

18

0 20 40 60

Turbidity Boundary (mg/mL Phenol)

Temperature (°C)

0.1

2.5

5

10

20

P188 

(mg/mL)

0 mg/mL BzOH
Conclusion

• Provide a range of stable 

concentrations for 

pharmaceutical use

• Pharmaceutical formulations 

typically:

- 0.2–0.6 mg/mL poloxamer 188

- 9 mg/mL benzyl alcohol

• Phenol < 7 mg/mL

0

2

4

6

8

10

12

14

0 20 40 60

Turbidity Boundary 

(mg/mL Phenol)

Temperature (°C)

Clear

Turbid

0.4 mg/mL P188

9 mg/mL BzOH

0

2

4

6

8

10

12

14

0 5 10

Turbidity Boundary 

(mg/mL Phenol)

Poloxamer 188 (mg/mL)

Clear

Turbid

9 mg/mL BzOH

30 °C

13

Temperature

Poloxamer 188
Acknowledgements

• Center for High Resolution Neutron 

Scattering, funding the SURF 

program at the NCNR

• Dr. Rachel Ford, amazing mentor

• The friendly scientists and staff at 

the NCNR

14
Experimental Design • Create samples varying 

phenol, poloxamer 188, and 

benzyl alcohol 

• Place in temperature bath • Record phase (T/C) at varying 

temperatures

• All samples repeated at least 

once for reproducibility

15
Effect of Poloxamer 188

• Below 0.05 mg/mL 

P188 opposite effect occurs

- In absence of poloxamer 

188 turbidity boundary ~80 

mg/mL phenol

- But poloxamer 188 

increases turbidity boundary

• Turbidity likely caused by 

micellization

0.2 mg/mL poloxamer 188 0.025 mg/mL poloxamer 188

*Not a fitted curve

Benzyl alcohol Poloxamer 188

6

7

8

9

10

0 0.2 0.4 0.6

Turbidity Boundary 

(mg/mL Phenol)

Poloxamer 188 (mg/mL)

30 °C

9 mg/mL BzOH

16
Polysorbate 80

Molecular weight: 1310 g/mol

Poloxamer 188

Molecular weight: 8780 g/mol

Polysorbate 20

Molecular weight: 1226 g/mol