pHEMA: An Overview for Biomedical Applications

Abstract

Poly(2-hydroxyethyl methacrylate) (pHEMA) as a biomaterial with excellent biocompatibility and cytocompatibility elicits a minimal immunological response from host tissue making it desirable for different biomedical applications. This article seeks to provide an in-depth overview of the properties and biomedical applications of pHEMA for bone tissue regeneration, wound healing, cancer therapy (stimuli and non-stimuli responsive systems), and ophthalmic applications (contact lenses and ocular drug delivery). As this polymer has been widely applied in ophthalmic applications, a specific consideration has been devoted to this field. Pure pHEMA does not possess antimicrobial properties and the site where the biomedical device is employed may be susceptible to microbial infections. Therefore, antimicrobial strategies such as the use of silver nanoparticles, antibiotics, and antimicrobial agents can be utilized to protect against infections. Therefore, the antimicrobial strategies besides the drug delivery applications of pHEMA were covered. With continuous research and advancement in science and technology, the outlook of pHEMA is promising as it will most certainly be utilized in more biomedical applications in the near future. The aim of this review was to bring together state-of-the-art research on pHEMA and their applications.

Keywords: antimicrobial strategies; biomedical application; cancer therapy; contact lens; ocular drug delivery; pHEMA; tissue engineering and regenerative medicine.

Figure 1

A schematic representing the synthesis of pHEMA hydrogel from copolymerization of HEMA with other co-monomers, (EGDMA, ethylene glycol dimethacrylate). Reprinted from [27] with permission from Taylor & Francis.

Figure 2

A schematic showing the preparation of thermosensitive polymer followed by wound healing (A); the in vivo results of different samples when they were applied on the wounds for 14 days (B); the antibacterial activity of samples against both Staphylococcus aureus and Escherichia coli bacteria (C); ammonium persulfate (APS), radical transformation (RT), poly-(HEMA-co-NIPAM) (PHN), reprinted from [11] with permission from Wiley. ** denotes p < 0.01.

Figure 3

A schematic showing different approaches toward drug delivery for cancer therapy—static (A), dynamic (B), and main mechanism for controlling drug release (C). Reprinted from [49] with permission from Elsevier.

Figure 4

A schematic of the micelle (A); TEM micrograph of the micelle (B); the release rate of doxorubicin-loaded micelle at physiological and acidic mediums (C); the positron emission tomography images of 4T1 tumor-bearing mice treated with ⁶⁴Cu-labeled targeted, non-targeted micelles, and targeted micelles with a blocking dose of TRC105 at different time intervals (D). Reprinted from [55] with permission from American Chemical Society.

Figure 5

The mechanism of the drug-loaded hydrogen sulfide-responsive micelles when exposed to the stimulant is depicted schematically (A); the drug release rates of the drug-loaded N3-Nap-pHEMA-b-PMMA-N3 sample at acidic and physiological environments, with/without being exposed to hydrogen sulfide (B); the images of HeLa cells treated with doxorubicin (a), drug-loaded N3-Nap-pHEMA-b-PMMA-N3 without hydrogen sulfide (b), and drug-loaded N3-Nap-pHEMA-b-PMMA-N3 with hydrogen sulfide (c), taken by confocal microscopy (scale bar = 20 μm) (C); the cell viability (%) of drug and non-loaded samples, with/without being exposed to hydrogen sulfide (D). Reprinted from [16], with permission from the American Chemical Society.

Figure 6

A schematic exhibiting the synthesis procedure of pHEMA-PMMA-magnetite (Fe₃O₄) (A); the TEM micrographs of the cross-linked pHEMA nanogel (chemically) (a), the cross-linked pHEMA microgel (physically and chemically) (b), Fe₃O₄-coated cross-linked pHEMA-methotrexate (c), pHEMA-PMMA-Fe₃O₄ (Janus) (d) (B); the release trends of methotrexate from pHEMA-PMMA-Fe₃O₄ nanoparticles (C); the magnetic hysteresis loops of bare Fe₃O₄ and final pHEMA-PMMA-Fe₃O₄ nanoparticles (a) plus separation of pHEMA-PMMA-Fe₃O₄ nanoparticles in water by a magnet (b) (D). Reprinted from [15], with permission from the American Chemical Society. (Red arrow: in Figure (b) show coagulation of cross-linked pHEMA nanogel).

Figure 7

Schematic representation depicting the difference in drug release time using contact lenses as compared to the conventional topical formulation.

Figure 8

Antimicrobial strategies to fabricate microbiocidal contact lenses.