Contact your particles with an aqueous solution of the drug and pray for it to enter the particles and become adsorbed. It is probably easier yo prepare your own particles, that way you can encapsulate the drug. 

Hi Ashleigh,

you can use double emulsion technique. 

• Dissolution of 30 mg of poly(D,L-lactide-co-glycolide) (PLGA) in 1 mL of chloroform at 4°C.
• Preparing 10mg/ml of drug solution into water under alkaline conditions using 0.5 M NaOH.
• Adding drug solution into PLGA/Chloroform solution at a concentration of 0.5, 1.0, 1.5 and 2.0 mg/ml. Formation of primary emulsion occurs by vortexing for 20 seconds, followed by tip sonication at 60W for 1 minute.
• Preparing 2 mL of a 2% w/v poly(vinyl alcohol) (PVA) / distilled deionized water solution. Upon solubilization of the PVA in water, 1 mL of ethanol or methanol need to be add as a non-solvent to the PVA solution.
• Adding primary emulsion into PVA/ethanol solution at rate of 20 microleter-20 sec. to initiate formation of the secondary emulsion.
•  Vortexing emulsion for 20sec followed by tip sonication at 55W for 2 minutes.
•  For solvent evaporation half an hour stirring followed by 12 minutes vacuum evaporation at 37oC.
• Final filtration of sample using 0.45 um millipore filter and centrifugation at 15000g for 30 min. Samples can also be lyophilized with concomitant addition of cryoprotectant and lyoprotectant. 
• After lyophilization storage of sample at  4°C. Upon use reconstitution can be applied in PBS buffer.

This whole protocol was fully optimized by our lab. Addition of chloroform is optional as DCM can be used but solubility of hormones in chloroform justifies its use. Dispersion of hydrophobic drug in water is needed because direct addition into PLGA/Chloroform results into Clump formation or aggregation,observed during final reconstitution of formulation into PBS solution. Adding ethanol in PVA is also necessary as it prevents the precipitation of drug in PVA solution. 

You can follow these patents for further study

https://www.google.com/patents/EP2146694A1?cl=en

https://www.google.com/patents/US20120052041

But for my opinion single use of PLGA does not meet full requirement as its poor aqueous solubility is bigger issue so it's better to use phospholipid along with PLGA as it allows micellization and easy transport in plasma just like chylomicrons. Even PLGA -PEG-PLGA / PEG-PLGA-PEG also available for increasing solubility but their use cannot be justified due to lower entrapment due to steric hindrance.

Follow below link for phospholipid-PLGA particles

https://www.google.co.in/patents/US9138411

Hi Ashleigh,

I wouldn't choose the Double Emulsion method for a Hidrophobic drug.

In my opinion, you can either incubate the microspheres with your drug (but you will probably get low encapsulation efficiencies), or synthetise new particles with PLGA using the nanoprecipitation solvent difusion method (which will give you better yields).It is known that the nanoprecipitation is the best way to encapsulate hidrophobic drugs, rather than double emulsion method.

thank you all very much!

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