**A Comparative Study of the E**ff**ect of Di**ff**erent Stabilizers on the Critical Quality Attributes of Self-Assembling Nano Co-Crystals**

### **Bwalya A. Witika 1, Vincent J. Smith 2 and Roderick B. Walker 1,\***


Received: 17 January 2020; Accepted: 11 February 2020; Published: 23 February 2020

**Abstract:** Lamivudine (3TC) and zidovudine (AZT) are antiviral agents used orally to manage HIV/AIDS infection. A pseudo one-solvent bottom-up approach was used to develop and produce nano co-crystals of 3TC and AZT. Equimolar amounts of 3TC dissolved in de-ionized water and AZT in methanol were rapidly injected into a pre-cooled vessel and sonicated at 4 ◦C. The resultant suspensions were characterized using a Zetasizer. The particle size, polydispersity index and Zeta potential were elucidated. Further characterization was undertaken using powder X-ray diffraction, Raman spectroscopy, Fourier transform infrared spectroscopy, differential scanning calorimetry, and energy dispersive X-ray spectroscopy scanning electron microscopy. Different surfactants were assessed for their ability to stabilize the nano co-crystals and for their ability to produce nano co-crystals with specific and desirable critical quality attributes (CQA) including particle size (PS) < 1000 nm, polydispersity index (PDI) < 0.500 and Zeta potential (ZP) < −30 mV. All surfactants produced co-crystals in the nanometer range. The PDI and PS are concentration-dependent for all nano co-crystals manufactured while only ZP was within specification when sodium dodecyl sulfate was used in the process.

**Keywords:** nano co-crystals; crystal engineering; polydispersity index; zeta potential; particle size; zidovudine; lamivudine; HIV/AIDS; sonochemistry
