Table 1 Bench experiments summary

Everts, 2006 [24]

In vitro (N = 10)

To compare properties of BC-PRP prepared using three different commercially available devices that are used to prepare platelet gel, specifically focused on the most important platelet growth factors and WBC-derived MPO

BC-PRP versus whole blood

Not studied

* Platelet and WBC yield was significantly increased by ECS and GPS

* Nonsignificant increase in platelet and WBC count with AGF

* Significant increase in TGF-β1 and PDGF level in PG samples after activation of the E-CS or GPS samples

* No change in TGF-β1 and PDGF level in PG samples ECS-AGF samples

* No significant differences between MPO concentrations in BC-PRP and whole blood

* MPO concentration in the BC-PRP was significantly increased versus baseline (P < 0.001), indicating WBC activation before PG formation

*No correlation of MPO release and cellular count

Healthy donors

Statistics are unclear, could have randomized blood volunteers to devices

Bielecki, 2007 [38]

In vitro (N = 20)

To analyze antibacterial effect of PRP gel in vitro

PRP gel versus thrombin

* MRSA

* MSSA

* Escherichia coli

* K. pneumoniae

* E. Faecalis

* P. aeruginosa

* PRP gel inhibited growth of S. aureus and E. coli

* There was no activity against K. pneumoniae, E. faecalis, and P. aeruginosa

* PRP gel seemed to induce in vitro growth of Aeruginosa, suggesting that it may cause an exacerbation of infections with this organism

* No correlation between antimicrobial activity and concentration of platelets and leukocytes

Review paper

Moojen, 2008 [39]

In vitro (N = 6)

To investigate antimicrobial activity of PLG against S. aureus and the contribution of MPO present in leukocytes in this process

PLG versus PPP

S. aureus

* PLG-AT, PLG-BT, PRP inhibited the growth of S. aureus

* There was release of MPO as early as 4 h in PLG-AT, PLG-BT, and PRP; MPO release was maximum at 8 h compared to PPP

* No correlation between antimicrobial activity and MPO release and MPO activity

Unclear if blood from individual donors was pooled. No control for individual donor demographics or inclusion/exclusion criteria. Healthy donors may not translate to sick population

Tohidnezhad, 2012 [40]

In vitro (N = 14)

To investigate secretion of antimicrobial peptides by thrombocytes to elucidate the mechanism of thrombocyte anti-infective capabilities

PRP versus PRP

* B. megaterium

* P. mirabilis

* Escherichia coli

* E. coli

* K. pneumonia

* E. faecalis

* PRP inhibited growth of S. aureus, E. coli, B. megaterium (P < 0.036), P. aeruginosa (P < 0.008), and E. faecalis (P < 0.001) and not P. mirabalis

* hBD-3 concentration is significantly increased in PRP and PPP supernatant after activation and might act as first line defense

Young healthy donors may not translate. Pooled blood from the individual healthy donors. No control for individual demographics or inclusion/exclusion criteria

Tohidnezhad, 2011 [23]

In vitro (N = 24)

To investigate release of hBD-2 by platelets as a local antibacterial agent

PRP

PRGF versus PPP

* B. megaterium

* P. mirabilis

* Escherichia coli

* E. coli

* K. pneumonia

* E. faecalis

* PRP inhibited growth of E. coli, B. megaterium, P. aeruginosa, E. faecalis, and P. mirabilis

* hBD-2 concentration is significantly increased in PRP compared to PPP and PRGF

* Preincubation of E. coli and P. mirabilis significantly decreased antibacterial effect of PRP in these strains

Pooled blood from individual healthy donors expired platelets. No control for individual donor demographics or inclusion/exclusion criteria

Burnouf, 2013 [30]

In vitro (N = 2)

To compare the antimicrobial activity of four distinct plasma and platelet materials from 2 donors against 4 g-positive and 4 g-negative bacteria that can colonize wounds, and to elucidate which component in PG preparation can inhibit wound bacteria

PRP supernatant PG S/D-PL versus Inactivated PRP

* P. aeruginosa

* E. coli

* E. cloacae

* K. pneumoniae

* B. cereus

* B. subtilis

* S. aureus

* S. epidermidis

* E. coli colony was strongly inhibited with native PRP, PPP, PG, and S/D-PL at 3 h

* P. aeruginosa count was strongly reduced in native PRP, PG, and S/D-PL (4.62, 4.61, and 4.80 log, respectively) but much less in PG (1.10 log)

* After 3 h, there was regrowth of P. aeruginosa in all PRP preparations

* K. pneumoniae was strongly inhibited in native PRP, PPP, and S/D-PL (6.71, > 7.71, and 6.71 log, respectively)

and less in PG (4.63 log)

* E. cloacae growth was less affected by the plasma and platelet preparations (reduction close to or < 1 log)

*Growth of the 4 g-negative bacteria was not inhibited when preparations were heat-treated to inactivate complement, suggesting the role of complement in bacterial inhibition

*By contrast, a close to 100-fold inhibition of S. aureus was seen with native PRP, PPP, and S/D-PL (1.50, 2.10, and 1.80 log, respectively) but not with PG (0.23 log)

Healthy volunteers, no donor information, no inclusion/exclusion criteria

Li, 2013 [42]

Ex vivo (N = 50)

To investigate antibacterial property of L-PRP gel against MRSA in a rabbit model of osteomyelitis

L-PRP gel versus no treatment control

MRSA

*There was an increase in the concentrations of the 4 growth factors in the activated PRP versus whole blood and non-activated PRP

*The highest VEGF levels in L-PRP gel supernatants were detected 1 h after activation (5.0-fold increase)

*The highest PDGF-BB concentrations were observed in PRP supernatants 3 days after activation

(3.4-fold increase), whereas TGF-β1 concentrations was highest at 1 day after activation

*IGF-1 concentrations in supernatants from non-activated PRPs were higher than activated samples

* Infection rate of control group was significantly higher than vancomycin (P = 0.035), L-PRP gel with vancomycin (P = 0.02), and L-PRP gel only (P = 0.088)

* L-PRP gel could promote bone regeneration effectively only when infection was controlled

No increase in growth factors or cytokines in unactivated PRP versus whole blood except for IGF-1

Aktan, 2013 [25]

In vivo (N = 5)

To investigate equine platelets on bacterial growth, their ability to release products with antimicrobial properties or to influence the antimicrobial actions of neutrophils

L-PRP gel versus PRP and PPP, PBS

* E. coli

* S. aureus

* PRP and PPP inhibited growth of E. coli and the effect was more prominent with activated PRP at 0.5 and 2 h

* Phorbol myristate acetate stimulated platelets and caused increased superoxide production; significant platelet superoxide production was not observed in response to strong platelet stimuli such as thrombin and platelet activated factor

* LPS and LTA activated platelets as measured with increased P-selectin expression

* LPS and LTA had no effect on platelet superoxide production or heterotypic aggregate formation

* Coincubation of activated platelets with neutrophils did not increase neutrophil superoxide production

Equine

Li, 2013 [41]

In vitro and ex vivo (N = 5)

To evaluate the antimicrobial and wound healing properties of PRP in spine infection rabbit model

PRP versus PBS

* MSSA

* MSRA

* Group A streptococcus

* Neisseria gonorrhoeae

* PRP treatment has no significant antimicrobial effects against E. coli and Pseudomonas

* PRP could significantly (80–100 fold reduction in CFUs at 200 IU/mL thrombin) inhibit the growth of MSSA, MRSA, Group A Streptococcus, and Neisseria gonorrhoeae within the first 2 h

* The concentration of thrombin played a role in the antimicrobial properties of PRP; the higher the thrombin concentration (over the range of 20 to 200 IU/mL), the better the antimicrobial properties

* PRP showed the capability to improve bone healing in the presence of a severe infection

Rabbit spine

Różalski, 2013 [31]

In vitro (N = 5)

To evaluate microbicidal activity of platelets and their products against S. aureus in suspension (planktonic) and sessile (biofilm) cultures

PRP (Expired: 1–3 post shelf life) versus Müller–Hinton agar

* S. aureus

* Microbicidal activity of “expired” platelets and their lysates has been shown as a significant reduction in the population of staphylococci in their planktonic cultures by 56–87% and a decrease in metabolic activity of biofilm formation by 7–38%

* Antibacterial effect was enhanced after activation with ADP

* Platelet lysates showed a synergistic effect with β-lactam antibiotic (oxacillin) and glycopeptide (vancomycin) but not with oxazolidinone (linezolid)

No control for donors, pooled many donors, expired platelets

Edelblute, 2014 [43]

In vitro and ex vivo (N = 3–7)

To quantify efficacy of human platelet gel against opportunistic bacterial wound pathogens A. baumannii, P. aeruginosa, and S. aureus on skin

PRP versus quiescent platelet pellet (minimally manipulated)

* A. baumannii * P. aeruginosa

* S. aureus

* A. baumannii was significantly (P < 0.001) inactivated by both control and activated PG supernatants

* S. aureus was significantly (P < 0.05) inactivated only by the thrombin- and PEF-activated supernatants

* No significant inactivation was observed in the quiescent or CaCl₂ enriched groups

* P. aeruginosa was not inactivated in vitro; a low but significant inactivation level was observed ex vivo

* PRP supernatants were quite effective at inactivating a model organism on skin in vivo

Well designed, expired platelets, multiple donors

Intravia, 2014 [28]

In vitro (N = 2)

To investigate antibacterial properties of 2 PRP: platelet concentration preparations (PRP-LP and PRP-HP)

* PRP-LP: lower WBCs and platelet concentration

* PRP-HP: high platelet and WBC concentration vs

* Blood + PBS (negative control)

* Cefazolin (positive control)

* S. aureus

* S. epidermidis

* MRSA

* P. acnes

* Both PRP-LP and PRP-HP showed a significant decrease (P < 0.05) in bacterial growth at 8 h compared to whole blood

* There was no statistically significant difference between PRP-LP or PRP-HP and cefazolin at 24 h

* The effect of PRP-LP and PRP-HP on P. acnes and MRSA was minimal and may not be clinically significant

* Despite differences in platelet and WBC concentrations, no difference in antibacterial activity was seen between PRP-LP and PRP-HP preparations

Two healthy donors; low sample size, and healthy PRP may not translate

Frelinger, 2016 [9]

In vitro (N = 5)

To compare the ability of PEF, bovine thrombin, and TRAP to activate human PRP, release growth factors, and induce cell proliferation in vitro

PRP versus PRP treated with 0.9% sodium chloride, PPP

Not studied

* Both PEF and bovine thrombin reduced the average size of platelet-related (CD41-positive) particles, but the number of detectable CD41-positive particles after PEF activation was significantly higher than after bovine thrombin activation

* Surface P-selectin was increased on particles following PEF activation but was increased to a greater extent by bovine thrombin and TRAP

* PEF activation produced a higher number of procoagulant annexin V-positive particles. The total annexin V binding (a measure of phosphatidylserine expression) was similar after PEF and bovine thrombin activation

* PEF activation of fresh PRP resulted in greater release of EGF than activation with bovine thrombin, whereas only TRAP activation resulted in significant release of angiostatin

* Plasma containing the releasate from PEF-activated PRP induced significantly greater proliferation of an epithelial cell line than plasma recovered from vehicle-treated PRP

Healthy donors may not translate

Mariani, 2015 [14]

In vitro (N = 10)

To compare in vitro microbicidal activity of platelets and L-PRP to P-PRP and the contribution of leukocytes to microbicidal properties

PRP versus L-PRP cryo and P-PRP

* E. coli

* S. Aureus

* K. pneumoniae

* P. aeruginosa

* E. faecalis

* L-PRP, L-PRP cryo and P-PRP generally induced comparable bacterial growth inhibition for up to 4 h incubation

* The concentrations of soluble factors considered (MIP-1α/CCL3, RANTES/CCL5, GRO-α/CXCL1, NAP-2/CXCL7, IL-8/CXCL8, SDF-1α/CXCL12 and IL-6) were strongly correlated to bacterial growth inhibition, mainly from the second hour of incubation

* E. coli inhibition showed correlations with RANTES, GRO-α, and SDF-1α concentrations (P ≤ 0.05)

* S. aureus inhibition correlated with the concentrations of all the molecules excluded IL-6 (P ≤ 0.05)

* K. pneumoniae, P. aeruginosa, and E. faecalis inhibition correlated with the concentrations of all microbicidal molecules considered (P ≤ 0.05)

* L-PRP and L-PRP cryo exhibited similar microbicidal activity

Healthy donors may not translate, correlation of bacterial growth to soluble factors

Lu, 2016 [36]

In vitro and ex vivo

To examine effects of a combined chitosan–gelatin sponge loaded with tannins and PRP (CSGT-PRP) on extent and rate of wound healing, antibacterial effects of the sponge, and stability of the wound dressing material

PDGF isolated from thrombocyte concentrate versus wound dressing and PRP, CSGT-PRP

* E. coli

* S. aureus

* CSGT-PRP had good thermostability and mechanical properties as well as efficient water absorption and retention capacities

* CSGT-PRP could effectively inhibit the growth of E. coli and S. aureus with low toxicity

* CSGT-PRP healed wound quickly as observed macroscopically and by histological examinations

Healthy animals’ PRP may have different properties than those from infected animals

Bayer, 2016 [21]

In vitro and ex vivo

To determine if Chitosan composite hydrogel system is an effective medium for antibiotic delivery in wound infection caused by S. aureus

Vivostat PRF® (thrombocyte concentrate) versus 0.9% sodium chloride

None

* PRGF increases hBD-2 expression in concentration- and time-dependent manner

* PRGF mediated hBD-2 expression was mediated through EGFR and interleukin receptor (IL-6)

* hBD-2 indication through PDGF required activation of transcription factor activator protein (AP-1), but not through nuclear factor kappa ĸB

* Vivostat PRF mediated wound healing is mediated through hBD-2 expression

Healthy donors, no demographic information on the donors

Nimal, 2016 [47]

In vitro

To develop a novel injectable hydrogel system for infectious wound treatment that can reduce the inflammatory phase (by inhibiting bacterial growth using tigecycline) and enhance the granulation phase (by addition of PRP) and simultaneously promote efficient wound healing

PRP from blood bank versus Tigecycline nanoparticles + chitosan hydrogel in PBS

S. aureus

* tg-ChPRP gel, and tg-ChNPs-ChPRP gel showed a significant zone of inhibition against S. aureus

* ChPRP gel alone failed to demonstrate any antibacterial activity, and the incorporation of PRP in to the tg-Ch and tg-ChNPs-Ch gel did not enhance or inhibit antibacterial activity

* ChPRP gel with the lowest concentration of tg-ChNPs (1 μg/mg) also showed a significant reduction in bacterial growth

No information on donor blood from blood bank; assume healthy non-infected donors

Knafl, 2017 [33]

In vitro (N = 5)

To evaluate release kinetics of amikacin, teicoplanin, or polyhexanide from a PRF layer

PRF versus Trypsin only and PRF only (negative control)

* MSSA

* MRSA

* P. aeruginosa

* K. pneumoniae

* Teicoplanin and amikacin released from PRF showed antimicrobial in vitro effects for almost a week

* Antimicrobial effect of polyhexanide could only be verified for the first 24 h

Small sample size and limited information on donor plasma

Bayer, 2018 [34]

In vitro

To demonstrate that PRGF induces antimicrobial peptides in primary keratinocytes and accelerates keratinocyte proliferation

Vivostat PRF® versus untreated using normal human epidermal keratinocytes cells

None

* PRGF stimulation caused a significant decrease in the Ki-67 gene expression in human primary keratinocytes, and EGFR is not essential to the PRGF-mediated reduction of Ki-67 gene expression in human primary keratinocytes

* The interleukin-6 receptor (IL-6R) is not essential to the PRGF-mediated reduction of Ki-67 gene expression in human primary keratinocytes

* IL-6 signaling is not involved in the PRGF-mediated reduction of the Ki-67gene expression in primary human keratinocytes

Healthy donors and no demographic information

Cetinkaya, 2018 [44]

Ex vivo (N = 72)

To investigate antibacterial activity and wound healing effectiveness of PRP in MRSA-contaminated superficial soft tissue wounds in Wistar Rats

PRP and vancomycin versus Sham, PRP, MRSA, MRSA + PRP, MRSA + vancomycin, MRSA + vancomycin + PRP

MRSA

* MRSA counts were lowest in MRSA + vancomycin + PRP groups

* Inflammation scores of MRSA + PRP, MRSA + vancomycin, and MRSA + vancomycin + PRP groups were significantly lower than the MRSA group

* The inflammation score was significantly lowest in MRSA + PPRP + vancomycin suggesting synergistic effect of vancomycin

No a priori sample size calculation

Cetinkaya, 2019 [45]

Ex vivo (N = 10)

To demonstrate in vitro antibacterial activity of PRP against MRSA and 3 more multi-drug resistant bacteria species that are important and hard-to-treat in wound infections

PRP gel versus PBS and PPP

* MRSA

* Enterococcus spp

* K. pneumoniae

* P. aeruginosa

* PRP and PPP significantly suppressed bacterial growth of MRSA, K. pneumoniae, and P. aeruginosa as early as 1st, 2nd, 5th, and 10th hours of incubation (P < 0.05) compared to control

* The antibacterial effect of PRP was more prominent compared to PPP

* PRP and PPP showed limited activity against VRE

Healthy donors may not translate to clinical use

Cieślik-Bielecka, 2019 [46]

In vitro (N = 20)

To evaluate the antimicrobial effect of L-PRP against selected bacterial strains and assess potential correlation with leukocyte and platelet concentrations

L-PRP versus acellular plasma

* S. aureus

* E. coli

* Cryptococcus neoformans

* Candida albicans

* L-PRP possesses an in vitro antimicrobial activity against MRSA, MSSA, E. faecalis, and P. aeruginosa

* L-PRP did not exert any antimicrobial activity against E. coli (extended spectrum beta lactamase), E. coli, and K. pneumoniae

* A relationship was observed among selected leukocyte subtypes (T and B lymphocytic NK cells, monocytes, and granulocytes with CD45) and L-PRP antimicrobial activity

Healthy donor plasma may not have properties of patients who have infection

Li, 2019 [29]

In vitro (N = 21)

To examine the potential mechanism underlying roles of PRP in treating diabetic foot ulcers

PRP and extract liquid of PRG versus PPP

* S. aureus

* PRG and EPG exhibited antibacterial effect against S. aureus

* PRG and EPG protect HaCaT cells from bacterial damage and promote cell proliferation

* Incubation of HaCaT cells with S. aureus decreased cell proliferation

* The level of programmed cell death factor 4 and activity of NF-κB were increased in HaCaTcells with concomitant increased IL-6, TNF-α and decreased IL-10, TGF-β1 in cultured supernatant

* EPG increased intracellular miRNA-21 while reducing PDCD4 expression and inhibiting NF-κB activity to suppress the inflammation in HaCaT cells

* Both PRG and EPG had a significant reduction in bacterial count within 12 h (P < 0.01) compared to control

Used PRP from patients with infected foot ulcers

Ikono, 2018 [49]

In vitro

To assess use of chitosan-PRP nanoparticles to improve the viability of PRP and prolonged release of growth factors

Chitosan-PRP nanoparticles

S. mutans

* Chitosan PRP nanoparticles had strong antibacterial activity against S. mutans (90.63% inhibition), suggesting a novel mechanism to deliver PRP in wounds to promote healing

No data on donors