Emerging Strategies to Enhance Solubility of Poorly Soluble Drugs: From Nanosystems to Molecular Innovations

A special issue of Pharmaceutics (ISSN 1999-4923). This special issue belongs to the section "Physical Pharmacy and Formulation".

Deadline for manuscript submissions: 31 January 2026 | Viewed by 1022

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Guest Editor
Department of Pharmaceutics and Drug Delivery, School of Pharmacy, The University of Mississippi, Oxford, MS 38677, USA
Interests: drug delivery systems; biodegradable polymers; nanomedicine; 3D printing in pharmaceutics; hot-melt extrusion
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Special Issue Information

Dear Colleagues, 

The poor aqueous solubility of many APIs remains a major challenge in drug development, often restricting bioavailability and therapeutic effectiveness. This Special Issue will cover various innovative strategies developed over the past decade to improve the solubility and dissolution rate of poorly soluble drugs. New approaches include nanonization techniques such as those incorporating nanocrystals and solid lipid nanoparticles, the employment of amorphous solid dispersions, cyclodextrin complexation, co-crystallization, and the use of ionic liquids and deep eutectic solvents. Additionally, molecular-level innovations including those in prodrug design and salt formation will be discussed, alongside advances in formulation technologies such as 3D printing and hot-melt extrusion.

Dr. Sateesh Kumar Vemula
Guest Editor

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Keywords

  • poorly soluble drugs
  • solubility enhancement
  • nanotechnology
  • amorphous solid dispersions
  • cyclodextrin complexation
  • co-crystallization
  • ionic liquids
  • deep eutectic solvents
  • prodrug design
  • formulation technologies

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Published Papers (2 papers)

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Research

25 pages, 6041 KB  
Article
Formulation and Evaluation of Alginate Microcapsules Containing an Uncompetitive Nanomolar Dimeric Indenoindole Inhibitor of the Human Breast Cancer Resistance Pump ABCG2 with Different Excipients
by Krisztina Bodnár, Christelle Marminon, Florent Perret, Ádám Haimhoffer, Boglárka Papp, Pálma Fehér, Zoltán Ujhelyi, Joachim Jose, Marc Le Borgne, Ildikó Bácskay and Liza Józsa
Pharmaceutics 2025, 17(12), 1587; https://doi.org/10.3390/pharmaceutics17121587 - 9 Dec 2025
Abstract
Background/Objectives: The ABCG2 transporter actively effluxes anticancer drugs, reducing their efficacy and promoting multidrug resistance (MDR). Developing oral formulations of poorly soluble ABCG2 inhibitors remains challenging due to their low solubility and intestinal permeability. This study aimed to formulate and evaluate an [...] Read more.
Background/Objectives: The ABCG2 transporter actively effluxes anticancer drugs, reducing their efficacy and promoting multidrug resistance (MDR). Developing oral formulations of poorly soluble ABCG2 inhibitors remains challenging due to their low solubility and intestinal permeability. This study aimed to formulate and evaluate an ABCG2 inhibitor using micro- and nanoscale drug delivery systems. Methods: To address the poor solubility and bioavailability of the corresponding active ingredient, a self-nanoemulsifying drug delivery system (SNEDDS) was developed. The SNEDDS was encapsulated into microcapsules using sodium alginate crosslinked with calcium chloride. Five microcapsule formulations were developed, varying in the inclusion of polyvinylpyrrolidone (PVP), Transcutol® HP and SNEDDS. The effects of the excipients on encapsulation efficiency, swelling capacity, enzymatic stability, dissolution, cytocompatibility, and permeability were systematically evaluated. Results: The SNEDDS exhibited monodisperse particle sizes and efficient drug entrapment. Results revealed that formulations incorporating PVP and SNEDDS improved encapsulation efficiency and bioavailability. SNEDDS-containing formulations demonstrated superior enzymatic stability in simulated gastric and intestinal fluids and provided the highest cumulative drug release in vitro. Cytotoxicity studies conducted on Caco-2 and MCF-7 cells demonstrated that our formulations were well tolerated, indicating favorable biocompatibility. Conclusions: Our findings demonstrate that SNEDDS-loaded alginate microcapsules offer an efficient platform for oral delivery of dimeric ABCG2 inhibitors, combining enhanced solubility, stability, and controlled release. The optimized formulation can be regarded as a promising strategy to enhance the oral bioavailability of efflux pump inhibitors and other poorly soluble drugs. Full article
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17 pages, 1953 KB  
Article
Investigating the Potential of Poly(2-ethyl-2-oxazoline) and Its Polymer Blends for Enhancing Fenofibrate Amorphous Solid Dispersion Dissolution Profile
by Ziru Zhang, Rasha M. Elkanayati, Sheng Feng, Indrajeet Karnik, Sateesh Kumar Vemula and Michael A. Repka
Pharmaceutics 2025, 17(10), 1238; https://doi.org/10.3390/pharmaceutics17101238 - 23 Sep 2025
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Abstract
Background/Objectives: This study aimed to develop a novel amorphous solid dispersion (ASD) platform using poly(2-ethyl-2-oxazoline) (PEtOx) for the solubility enhancement of poorly water-soluble drugs. Fenofibrate (FB), a Biopharmaceutics Classification System (BCS) Class II drug, was selected as the model drug. The novelty of [...] Read more.
Background/Objectives: This study aimed to develop a novel amorphous solid dispersion (ASD) platform using poly(2-ethyl-2-oxazoline) (PEtOx) for the solubility enhancement of poorly water-soluble drugs. Fenofibrate (FB), a Biopharmaceutics Classification System (BCS) Class II drug, was selected as the model drug. The novelty of this work lies in the formulation of dual-matrix systems by blending PEtOx of varying molecular weights (50 kDa, 200 kDa, 500 kDa) with solubility-enhancing polymers, Soluplus® and Kollidon® VA64, to investigate component compatibility, synergistic solubility enhancement, and the influence of PEtOx molecular weight on drug release. Methods: ASDs were prepared via hot-melt extrusion (HME) and characterized using differential scanning calorimetry (DSC), scanning electron microscopy (SEM), powder X-ray diffraction (PXRD), and Fourier transform–infrared spectroscopy (FTIR) to confirm FB amorphization and evaluate drug–polymer interactions. In vitro dissolution testing was performed to assess drug release performance, and stability studies were conducted at ambient conditions for one month to evaluate physical stability. Results: DSC, PXRD, and FTIR confirmed the successful amorphization of FB and good miscibility between PEtOx and the selected excipients. In vitro dissolution studies showed an 8–12-fold increase in FB release from ASDs compared to crystalline drug. Lower-molecular-weight PEtOx grades yielded faster release profiles, while binary blends with Soluplus® or Kollidon® VA64 enabled tailored drug release. Stability testing indicated that all formulations maintained their amorphous state over one month. Conclusions: PEtOx-based ASDs represent a versatile platform for enhancing the solubility and dissolution of poorly water-soluble drugs. By adjusting polymer molecular weight and combining with complementary excipients, release profiles can be optimized to achieve improved performance and stability. Full article
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