TABLE 2.

Overview of the use of synthetic polymers for bacteriophage embedding.

Envisioned application	Polymer and construct	Embedded phage	Relevant results				Reference
			Study type	Manufacturing process and Protective properties	Phage release	Antimicrobial effects
Protection of phage against acidic gastric environment	Microcapsules of anionic methacrylic acid and methyl methacrylate copolymer (Eudragit® S100) and trehalose.	S. enterica phage Felix O1	In vitro	Phages exposed to high temperatures during spray drying (100–180°C) with low titer loss. Copolymer: trehalose (2:1 ratio) showed high phage loading and acid resistance. Dry storage (RT, 3 months) caused 1log10 titer reduction.	Encapsulation of 109 PFU/gram was achieved. Presence of trehalose prevented a 4log10 reduction observed for copolymer formulations.	Not assessed	Vinner et al., 2019
Food preservation by incorporation in packaging material	Hollow fibers mats of poly (ethylene oxide) (PEO) and cellulose diacetate (CDA) blends.	E. coli phage T4	In vitro	PEO and CDA were dissolved in 98:2 wt% chloroform/methanol. Fiber mats were fabricated by coaxial electrospinning. Fiber diameter range 1.35–2.47 μm, containing internalized phage.	Higher PEO MW equals slower phage release kinetics. Increase of hydrophobic CDA slows fiber swelling and thus phage release kinetics.	Not assessed	Korehei and Kadla, 2014
Treatment of bacterial lung infections	W1/O/W2 Microparticles of PLGA and Pluronic 92L, fabricated by W/O/W emulsions	S. aureus phage and an isolated P. aeruginosa phage	In vitro	W1: 1% aqueous solution of Pluronic 92L, O: 5% PLGA solution in DCM, W2: 1% aqueous PVA solution. Both W1 and W2 contained phage. Emulsions were mixed by homogenizer. Microparticles were frozen in liquid N2 and lyophilized without cryoprotectants.	Encapsulated phage in W1 did not efficiently release. W1 and W2 combined phage release reached 15% and 25% of encapsulated S. aureus and P. aeruginosa phage, respectively.	Lytic activity of both S. aureus and P. aeruginosa phage prevented bacterial lawn formation after 1- or 3-days storage at room temperature. No PFU observed after 7 days dry storage at 4°C or RT.	Puapermpoonsiri et al., 2009
Treatment of root canal infections	Poloxamer P407 hydrogel (30% w/v)	E. faecalis phages EFDG1 and EFLK1	In vivo	30% poloxamer P407 solution was made by directly dissolving the polymers in the phage cocktail dispersion (109 PFU/mL).	Hydrogel gelation occurred in 2–3 min after incubation at 37°C. Released phage gradually decreased over 28 days (from 108 PFU/mL to 104 PFU/mL).	In vitro CFU reduction of 3–4log10 reduction against biofilm cultures. In vivo efficacy in a rat model was proven against a 4-week old root canal infection (2log10 CFU reduction) and was superior to a single 109 PFU/mL administration of unembedded phage (1.5log10 CFU reduction).	Shlezinger et al., 2019
			Study type	Manufacturing process and Protective properties	Phage release	Antimicrobial effects
Delivery of phage to the lungs of cystic fibrosis patients	Hollow microparticles of poly (lactic-co-glycolic acid) (PLGA)	Multiple P. aeruginosa phages	In vivo	Porous PLGA microparticles with phage loading after particle formation. Phage load of 2.6⋅106 PFU/mg particle. Dry powder formulation by lyophilizing particles in lactose solutions.	Inhibitory zone of P. aeruginosa around phage loaded PLGA particles was microscopically observed, indicating phage release from the PLGA microparticle.	In vitro biofilm CFU reduction of 2.5log10. Mice inoculated with P. aeruginosa were treated by particle inhalation resulting in a 1.5log10 reduction of CFU compared to free phage administration. Survival rate upon treatment was 100% versus 13% for untreated control mice.	Agarwal et al., 2018
Prophylactic phage and antibiotic delivery on orthopedic implants (K-wires)	Hydroxypropyl methylcellulose (HPMC) coating on K-wires	MRSA phage MR-5	In vitro	2% and 4% HPMC solutions containing phage and/or linezolid were used for dip coating the K-wires.	From 2% HPMC coatings, release was observed for 48 h. For 4% HPMC coatings a release period of 96 h was reached.	Reduction of 3log10 of CFU adhered to the K-wire with HPMC-phage coating. Additive effect between linezolid and phage was evident (>4log10 reduction of adhered CFU) after 48 h.	Kaur et al., 2014
Prophylactic phage and antibiotic delivery on orthopedic implants (K-wires)	Hydroxypropyl methylcellulose (HPMC) coating on K-wires	MRSA phage MR-5	In vivo	4% HPMC solutions containing phage and/or linezolid were used for dip coating the K-wires.	In vivo release of phage was not tested. Outcome based on CFU reduction.	Bacterial load diminished fastest for antibiotics/phage combination. Phage, antibiotic and combined loaded HPMC coating resulted no CFU observed in the soft tissue surrounding the implant.	Kaur et al., 2016
Treatment of orthopedic infections	Hydrogel of 4-armed polyethylene glycol (PEG) functionalized with crosslinking moieties	P. aeruginosa phages ΦPaer4/ ΦPaer14. S. aureus phage ΦK	In vivo	4 arms of the PEG macromers were functionalized with crosslinkers or tissue adhesive peptides.	Phage release dictated by enzymatic hydrogel degradation. In presence of collagenase, 50% phage release observed in 8 h.	In vitro anti-biofilm experiments resulting in a 1log10 reduction in CFU. In vivo, a 0.5log10 reduction in CFU was observed 7 days after phage/hydrogel treatment.	Bean et al., 2014

Abbreviations - CDA: cellulose diacetate; CFU: Colony-forming unit; DCM: Dichloromethane; HPMC: Hydroxypropyl methylcellulose; MRSA: Multi-resistant Staphylococcus aureus; PEG: Poly(ethylene glycol); PEO: Poly(ethylene oxide); PFU: Plaque-forming unit; PLGA: Poly(lactic-co-glycolic acid); PVA: Poly(vinyl alcohol); RT: Room temperature.