Platelet Derived Biomaterials for Therapeutic Use: Review of Technical Aspects

Engineering the Immune Response to Biomaterials

Biomaterials are increasingly used as implants in the body, but they often elicit tissue reactions due to the immune system recognizing them as foreign bodies. These reactions typically involve the activation of innate immunity and the initiation of an inflammatory response, which can persist as chronic inflammation, causing implant failure. To reduce these risks, various strategies have been developed to modify the material composition, surface characteristics, or mechanical properties of biomaterials. Moreover, bioactive materials have emerged as a new class of biomaterials that can induce desirable tissue responses and form a strong bond between the implant and the host tissue. In recent years, different immunomodulatory strategies have been incorporated into biomaterials as drug delivery systems. Furthermore, more advanced molecule and cell-based immunomodulators have been developed and integrated with biomaterials. These emerging strategies will enable better control of the immune response to biomaterials and improve the function and longevity of implants and, ultimately, the outcome of biomaterial-based therapies.

Mesenchymal stem cells in PRP and PRF containing poly(3-caprolactone)/gelatin Scaffold: a comparative in-vitro study

Scaffold design is one of the three most essential parts of tissue engineering. Platelet-rich plasma (PRP) and platelet-rich fibrin (PRF) have been used in clinics and regenerative medicine for years. However, the temporal release of their growth factors limits their efficacy in tissue engineering. In the present study, we planned to synthesize nanofibrous scaffolds with the incorporation of PRP and PRF by electrospinning method to evaluate the effect of the release of PRP and PRF growth factors on osteogenic gene expression, calcification, proliferation, and cell adhesion of human bone marrow mesenchymal stem cell (h-BMSC) as they are part of scaffold structures. Therefore, we combined PRP/PRF, derived from the centrifugation of whole blood, with gelatin and Polycaprolactone (PCL) and produced nanofibrous electrospun PCL/Gel/PRP and PCL/Gel/PRF scaffolds. Three groups of scaffolds were fabricated, and h-BMSCs were seeded on them: (1) PCL/Gel; (2) PCL/Gel/PRP; (3) PCL/Gel/PRF. MTS assay was performed to assess cell proliferation and adhesion, and alizarin red staining confirmed the formation of bone minerals during the experiment. The result indicated that PCL/Gel did not have any better outcomes than the PRP and PRF group in any study variants after the first day of the experiment. PCL/gelatin/PRF was more successful regarding cell proliferation and adhesion. Although PCL/gelatin/PRP showed more promising results on the last day of the experiment in mineralization and osteogenic gene expression, except RUNX2, in which the difference with PCL/gelatin/PRF group was not significant.

Optimization of Platelet-Rich Plasma Preparation for Regenerative Medicine: Comparison of Different Anticoagulants and Resuspension Media

Platelet-rich plasma (PRP) has emerged as a promising therapy in regenerative medicine. However, the lack of standardization in PRP preparation protocols presents a challenge in achieving reproducible and accurate results. This study aimed to optimize the PRP preparation protocol by investigating the impact of two different anticoagulants, sodium citrate (SC) and ethylenediaminetetraacetic acid (EDTA), and resuspension media, plasma versus sodium chloride (NaCl). Platelet recovery rates were calculated and compared between groups, in addition to platelet activity and vascular endothelial growth factor (VEGF) released into plasma after PRP activation. The platelet recovery rate was higher with EDTA in comparison to SC (51.04% vs. 29.85%, p = 0.005). Platelet activity was also higher, with a higher expression of two platelet antibodies, platelet surface P-Selectin (CD62p) and PAC-1, in the EDTA group. The concentration of VEGF was higher with SC in comparison to EDTA (628.73 vs. 265.44 pg/mL, p = 0.013). Platelet recovery rates and VEGF levels were higher in PRP resuspended in plasma when compared to NaCl (61.60% vs. 48.61%, p = 0.011 and 363.32 vs. 159.83 pg/mL, p = 0.005, respectively). Our study reinforces the superiority of EDTA (as anticoagulant) and plasma (for resuspension) in obtaining a higher platelet recovery and preserving platelet functionality during PRP preparation.

Advances in Regenerative Medicine and Biomaterials

The low regenerative potential of the human body hinders proper regeneration of dysfunctional or lost tissues and organs due to trauma, congenital defects, and diseases. Tissue or organ transplantation has hence been a major conventional option for replacing the diseased or dysfunctional body parts of the patients. In fact, a great number of patients on waiting lists would benefit tremendously if tissue and organs could be replaced with biomimetic spare parts on demand. Herein, regenerative medicine and advanced biomaterials strive to reach this distant goal. Tissue engineering aims to create new biological tissue or organ substitutes, and promote regeneration of damaged or diseased tissue and organs. This approach has been jointly evolving with the major advances in biomaterials, stem cells, and additive manufacturing technologies. In particular, three-dimensional (3D) bioprinting utilizes 3D printing to fabricate viable tissue-like structures (perhaps organs in the future) using bioinks composed of special hydrogels, cells, growth factors, and other bioactive contents. A third generation of multifunctional biomaterials could also show opportunities for building biomimetic scaffolds, upon which to regenerate stem cells in vivo. Besides, decellularization technology based on isolation of extracellular matrix of tissue and organs from their inhabiting cells is presented as an alternative to synthetic biomaterials. Today, the gained knowledge of functional microtissue engineering and biointerfaces, along with the remarkable advances in pluripotent stem cell technology, seems to be instrumental for the development of more realistic microphysiological 3D in vitro tissue models, which can be utilized for personalized disease modeling and drug development. This chapter will discuss the recent advances in the field of regenerative medicine and biomaterials, alongside challenges, limitations, and potentials of the current technologies.

Platelet-rich plasma treatment in patients with refractory thin endometrium and recurrent implantation failure: A comprehensive review

Refractory thin endometrium and recurrent implantation failure are among the most challenging infertility-related factors hindering successful pregnancy. Several adjuvant therapies have been investigated to increase endometrial thickness and the pregnancy rate, but the treatment effect is still minimal, and for many patients, these treatment methods can be quite costly and difficult to approach. Platelet-rich plasma (PRP) is an autologous concentration of platelets in plasma and has recently been elucidated as a better treatment option for these patients. PRP is rich in cytokines and growth factors, which are suggested to exert a regenerative effect at the level of the injured tissue. Another advantage of PRP is that it is easily obtained from the patient’s own blood. We aimed to review the recent findings of PRP therapy used for patients with refractory thin endometrium and recurrent implantation failure.

The Efficacy of Platelet-Rich Fibrin in the Management of Chronic Nonhealing Ulcers of the Lower Limb

Introduction

Nonhealing ulcers have a huge burden on the patient, by having high morbidity in terms of chronic pain, partial or complete loss of function, mental health issues, and social isolation, and can have a massive financial burden on the patient. Various novel therapies have been developed to treat nonhealing ulcers. Platelet-rich fibrin (PRF) has been developed in the recent era initially in the dental world for treating oral ulcers. Now, the role of PRF is strongly established in treating nonhealing ulcers. PRF has an aggregate of a myriad of growth factors and cytokines that stimulate healing of the wounds. In this study, we have compared the efficacy of PRF in treating nonhealing ulcers of the lower limb against normal saline dressings.

Aims and objectives

This study aims to determine the efficacy of platelet-rich fibrin over normal saline dressings in the treatment of nonhealing ulcers of the lower limb by comparing the percentage reduction in the surface area of wounds after treatment in both groups.

Methods

Fifty patients with nonhealing ulcers were selected and randomly divided into two groups with 25 patients in each group. Cases were treated with PRF dressings weekly for a period of six weeks. Controls were treated with normal saline dressings weekly for a period of six weeks. The percentage reduction in the size of the ulcer after treatment was recorded in both groups and compared. Patients of age 18-60 with nonhealing ulcers of the lower limb of >12 weeks duration have been included in the study. Patients having wounds with active infection, wound size > 35 cm², uncontrolled diabetes, peripheral vascular disease with Ankle-Brachial Index < 0.9, osteomyelitis of the underlying bone, and immunocompromised state, and patients on antiplatelet drugs have been excluded from the study.

Results

The mean age of the patients included in the study was 42.88 ± 2.73 years. The mean initial surface of the wound​​​ was 14.95 ± 3.08 cm² among cases and 13.28 ± 2.83 cm² among controls. The mean surface area of the wound after six weeks was 1.59 ± 0.78 cm² among cases and 11.08 ± 2.74 cm² among controls. The mean percentage reduction in the wound size after six weeks of treatment was 89.3% among cases and is significantly higher than in the normal saline group (16.5%) (Mdn = 14.63, U = 23, p < 0.00001).

Conclusion

Platelet-rich fibrin is an emerging potential topical agent for the treatment of nonhealing ulcers of the lower limbs and is more effective than normal saline dressings and also has the advantage of being cost-effective.

Platelet-Rich Plasma as an Orthobiologic: Clinically Relevant Considerations

Platelet-rich plasma (PRP) is an autologous blood-derived product processed to concentrate platelets and the associated growth factors. PRP has been shown to be relatively well-tolerated and safe to use for a number of conditions in humans, equines, and canines. There are multiple commercial systems that have been validated for canine use. These systems use a variety of methodologies to produce a PRP product. However, PRP products have been shown to differ greatly between systems. Further study is needed to fully elucidate optimal component concentrations for various indications.

Single intra-articular injection with or without intra-osseous injections of platelet-rich plasma in the treatment of osteoarthritis knee: A single-blind, randomized clinical trial

BACKGROUND

Subchondral bony structure damage plays an essential role in the pathogenesis of osteoarthritis (OA) knee. An intra-articular injection cannot reach the damaged subchondral bony structure and treat its pathologies effectively. The objective of the study was to compare the clinical effects of single intra-articular injection with or without intra-osseous injections of PRP in the treatment of osteoarthritis (OA) knee.

METHODS

This was a single-blind, parallel-group, randomized clinical trial. Fifty patients, with OA knee (K&L grade III), with ages between 50 and 65 years, were randomly allocated into 'intra-osseous, intra-articular PRP' ('IO+IA-PRP') (n = 25) or 'intra-articular PRP' group ('IA-PRP') (n = 25). Patients in the 'IO+IA-PRP' group received 18 ml PRP injection, and the 'IA-PRP' group received 8 ml PRP injection. Intra-osseous injections were given at the tibial plateau (5 ml) and femoral condyle (5 ml), along with intra-articular knee injection (8 ml), under fluoroscopic guidance. Outcomes were measured using VAS-pain, the knee injury and osteoarthritis outcome score (KOOS), and the treatment satisfaction scale. All patients (n = 50) were followed up till six months.

RESULTS

The mean age was 57.12(4.27) years and 57.00(4.96) years in the 'IO+IA-PRP' and 'IA-PRP' groups. Both groups showed significant improvement in pain relief (VAS pain) and KOOS parameters: pain, symptoms, ADL function, sport and recreation function, and quality of life. Compared to the 'IA-PRP' group, the 'IO+IA-PRP' group showed a greater reduction of VAS pain at six months. However, no significant difference was obtained in VAS pain-relief between these two groups (p = 0.422) at six months. Similarly, at 6 months, in inter-group comparison, except 'sport and recreation function' (p < 0.05), no significant differences were obtained in mean-scores of KOOS parameters: pain (p = 0.514); symptom (p = 0.148), ADL-function (p = 0.991), QoL-(p = 0.376). Patients in the 'IO+IA-PRP' group complained of significant 'injection-associated' adverse events and consumed a greater number of Acetaphenomen.

CONCLUSIONS

Both groups showed significant improvement following the intervention. Intra-osseous PRP injections did not provide any additional benefit over intra-articular PRP injection until six months regarding pain relief and functional improvement.

Resolving the missing link between single platelet force and clot contractile force

Blood clot contraction plays an important role in wound healing and hemostasis. Although clot contraction is known to be driven by platelets, how single platelet forces relate to the forces generated by macroscopic clots remains largely unknown. Using our microfabricated high-throughput platelet contraction cytometer, we find that single platelets have an average force of 34 nN ( n = 10 healthy individuals). However, multiple bulk clot experiments predict a mean single platelet force lower than 0.5 nN. To resolve this discrepancy, we use a mesoscale computational model to probe the mechanism by which individual platelets induce forces in macroscopic clots. Our experimentally informed model shows that the number of platelets in the clot cross-section defines the net clot force. We provide a relationship between single platelet force and the clot force that is useful for better understanding of blood disorders associated with bleeding and thrombosis, and facilitates the development of platelet-based and platelet-mimetic biomaterials.

The benefit of platelet-rich plasma injection over institution-based physical therapy program in adhesive capsulitis patients with diabetes mellitus: prospective observational cohort study

Background

The objective of this study was to compare the efficacy of platelet-rich plasma (PRP) injection with an institution-based physical therapy (PT) program for adhesive capsulitis (AC) of the shoulder in patients with diabetes mellitus (DM).

Methods

A total of seventy diabetic patients with AC of the shoulder for <6 months were assigned to two groups: PRP group and PT group. In the PRP group, 35 patients were administered a single shot of PRP (4 mL) into the glenohumeral joint. In the PT group, 35 patients were given institution-based PT that included 10 30-minute sessions of planned PT over a 2-week period. After the interventions, all patients were prospectively followed for 12 weeks. Intensity of shoulder pain, function, and range of motion were assessed at baseline and then at 3, 6, and 12 weeks.

Results

Thirty-three patients in the PRP group and 32 in the PT group completed the 12-week study. At 12 weeks, patients who received PRP injections showed greater improvement in shoulder pain (p<0.001) than those recruited to the PT group. In the range of motion and shoulder function activities, patients in the PRP group showed significant improvement compared with the institution-based PT group (p<0.001). No significant complications were reported from any groups.

Conclusions

In a diabetic population, PRP injections significantly improved shoulder pain and function compared with an institution-based PT program for shoulder AC. Additionally, it is a safe and well-tolerated method for AC management for diabetic patients.

Amelioration of Nicotine-Induced Osteoarthritis by Platelet-Derived Biomaterials Through Modulating IGF-1/AKT/IRS-1 Signaling Axis

Besides inhalation, a few studies have indicated that the uptake of nicotine through air or clothing may be a significant pathway of its exposure among passive smokers. Nicotine is well known to exert various physiological impacts, including stimulating sympathetic nervous system, causing vascular disturbances, and inducing cell death. Therefore, we aimed to establish whether exposure of nicotine could induce articular cartilage degeneration in a mouse model of osteoarthritis (OA). We specifically assessed dose-dependent effect of nicotine in vitro to mimic its accumulation. Further, during the in vivo studies, mice subcutaneously administered with nicotine was examined for OA-associated pathologic changes. We found that nicotine significantly suppressed chondrocytes and chondrogenic markers (Sox, Col II, and aggrecan). Nicotine-treated mice also showed altered knee joint ultrastructure with reduced Col II and proteoglycans. After corroborating nicotine-induced OA characteristics, we treated this pathologic condition through employing platelet-derived biomaterial (PDB)-based regenerative therapy. The PDB significantly suppressed OA-like pathophysiological characteristics by 4 weeks. The mechanistic insight underlying this therapy demonstrated that PDB significantly restored levels of insulin-like growth factor 1 (IGF-1) signaling pathway proteins, especially pIGF-1 R, pAKT, and IRS-1, regulating extracellular matrix synthesis by chondrocytes. Taken together, the PDB exerts regenerative and reparative activities in nicotine-mediated initiation and progression of OA, through modulating IGF-1/AKT/IRS-1 signaling axis.

Platelet-rich plasma: a narrative review

The aim of this article was to synopsize platelet-rich plasma (PRP) use in musculoskeletal pathologies through evidence-based assessment of the preparation, classification, mechanism of action and applications of PRP, thereby answering which PRP type is best for each clinical indication.

The literature search was performed using Medline, EMBASE and Cochrane Reviews databases for papers containing the key terms “platelet-rich plasma” AND “orthopaedics” AND (“classification” OR “mechanism of action” OR “preparation” OR “clinical application”). Generated papers were evaluated for pertinence in following areas: preparation, classification, mechanism of action, clinical application within orthopaedics. Non-English papers were excluded. Included studies were evaluated for quality.

Sixty studies were included in our review. There are many commercial PRP preparation kits with differing component concentrations. There is no consensus on optimal component concentrations. Multiple PRP classifications exist but none have been validated. Platelet-rich plasma acts via growth factors (GFs) released from α-granules within platelets. Growth factors have been shown to be beneficial in healing. Grossly elevated concentrations of GFs may have inhibitory effects on healing. Multiple systematic reviews show efficacy of PRP in tendinopathies, early osteoarthritis, acute muscle injuries and in combination with rotator cuff repair and anterior cruciate ligament reconstruction.

The literature suggests leukocyte-rich PRP (L-PRP) is more beneficial in tendinopathies and pure PRP (P-PRP) is more beneficial in cartilage pathology. However, different PRP preparations have not been directly compared in any pathology. Classification of PRP type is frequently not stated in research. Standardization of PRP research parameters is needed to streamline findings and generate clear indications for PRP types to yield maximum clinical benefit.

Cite this article: EFORT Open Rev 2021;6:225-235. DOI: 10.1302/2058-5241.6.200017

Poly-(lactic acid) and fibrin bioactive cellularized scaffold for use in bone regenerative medicine: Proof of concept

Bone regenerative medicine (BRM) aims to overcome the limitations of conventional treatments for critical bone defects by developing therapeutic strategies, based on temporary bioactive substitutes, capable of stimulating, sustaining, and guiding tissue regeneration. The aim of this study was to validate the “proof of concept” of a cellularized bioactive scaffold and establish its potential for use in BRM. For this purpose, three-dimensional scaffolds of poly-(lactic acid) (PLA), produced by the additive manufacturing technique, were incorporated into a human platelet-rich plasma (PRP-h) fibrin matrix containing human infrapatellar fat pad mesenchymal stem cells (hIFPMSC). The scaffolds (PLA/finbrin-bioactive) were kept under ideal culture conditions in a medium free from fetal bovine serum and analyzed at 5 and 10 days by Scanning Electron Microscopy (SEM), Fourrier Transform Infrared (FTIR), Circular Dichroism and fluorescence microscopy. The results demonstrated the feasibility of obtaining a rigid, cytocompatible, and cellularized three-dimensional structure. In addition, PRP platelets and leukocytes were able to provide a bioactive environment capable of maintaining the viability of hIFPMSC into scaffolds. The results validate the concept of a customizable, bioactive, cellularized, and non-immunogenic strategy for application in BRM.

Release kinetic of pro- and anti-inflammatory biomolecules from platelet-rich plasma and functional study on osteoarthritis synovial fibroblasts

BACKGROUND AIMS

This study evaluated the release kinetics of numerous representative and less studied platelet-rich plasma (PRP) cytokines/chemokines with regard to the effects of various cellular compositions and incubation times. In addition, the biological effects of different PRPs on osteoarthritis synovial fibroblasts in vitro were tested.

METHODS

Peripheral whole blood was collected from healthy donors, and pure platelet-rich plasma (P-PRP), leukocyte-rich platelet-rich plasma (L-PRP) and platelet-poor plasma (PPP) were prepared for the analysis of the following biomolecules: IL-1β, IL-4, IL-6, IL-10, IL-17a, IL-22, MIP-1α/CCL-3, RANTES/CCL-5, MCP-3/CCL-7, Gro-α/CXCL-1, PF-4/CXCL-4, ENA-78/CXCL-5, NAP-2/CXCL-7, IL-8/CXCL-8, Fractalkine/CX3CL-1, s-CD40L P-PRP, L-PRP and PPP. Their effect on osteoarthritis synovial fibroblasts in vitro was tested by analyzing changes induced in both gene expression on a panel of representative molecules involved in physiopathology of joint environment and synthesis of IL-1β, IL-8 and hyaluronic acid.

RESULTS

This study demonstrated that among the 16 analyzed biomolecules, four were undetectable, whereas most of the detected biomolecules were more concentrated in L-PRP even when concentrations were normalized to platelet number. Despite the pro-inflammatory boost, the various PRP preparations did not alter synovial fibroblast gene expression of specific factors that play a pivotal role in joint tissue homeostasis and are able to induce anti-inflammatory (TIMP-1) biomolecules.

DISCUSSION

This study provides a set of reference data on the concentration and release kinetics of some less explored biomolecules that could represent potential specific effectors in the modulation of inflammatory processes and in tissue repair after treatment with PRP.

Platelet-Rich Fibrin in Coverage of Gingival Recession: A Systematic Review and Meta-Analysis

This systematic review and meta-analysis sought to evaluate the efficacy of platelet-rich fibrin (PRF) membranes versus subepithelial connective tissue grafts (SCTGs) in the coverage of Miller class I and II gingival recessions. After the inclusion and exclusion criteria were applied, the quality of seven articles (Cohen's Kappa = 0.9) was evaluated using the Jadad scale. The MEDLINE/PubMed, Cochrane, and Web of Science databases were consulted, and manual searches were performed in the most popular periodontics journals. The studies included considered a total of 122 patients, 203 surgical fields on which SCTGs were used, and 205 surgical fields on which PRF was used. The parameters analyzed were probing depth, clinical attachment level, gingival recession, and keratinized mucosa. The minimum follow-up period accepted was 6 months. A statistically significant difference between the SCTG and PRF groups was found only in the case of keratinized mucosa. However, gingival recession, clinical attachment level, and probing depth parameters in the PRF group were found to be statistically equal to those of the SCTG group (the gold standard) (p ≥0.05). PRF membranes were determined to be a promising alternative to autogenous gingival grafts in the treatment of Miller class I and II gingival recessions.

Single Intra-articular Platelet-Rich Plasma Versus Corticosteroid Injections in the Treatment of Adhesive Capsulitis of the Shoulder: A Cohort Study

OBJECTIVE

The aim of the study was to compare the effects of single intra-articular platelet-rich plasma (PRP) and corticosteroid (CS) injections in patients with adhesive capsulitis of the shoulder.

DESIGN

Patients aged 18-70 yrs of either sex, diagnosed with adhesive capsulitis of shoulder, with less than 6-mo duration, were included. In intra-articular corticosteroid (IA-CS, control) group, 30 patients received a single injection (4 ml) of IA-CS and in IA-PRP (test) group, 30 patients received single IA-PRP injection (4 ml) into the glenohumeral joint under ultrasound guidance. All patients were prospectively followed for 12 wks.

RESULTS

Twenty-eight patients in IA-PRP group and 27 in IA-CS group finished the entire 12-wk study period. At 12 wks, decrements in visual analog scale and total shoulder pain and disability index scores, in IA-PRP group, were 58.4 and 55.1, compared with 48.7 and 45.8 in IA-CS group. In range of movement, IA-PRP group showed significant improvement in passive abduction (-50.4 vs. -39.4), internal (-36.8 vs. -25.8), and external rotations (-35.4 vs. -25.9) compared with IA-CS group, respectively. No major complications were observed in any patients.

CONCLUSIONS

At 12-wk follow-up, a single dose of IA-PRP injection was found to be more effective than an IA-CS injection, in terms of improving pain, disability, and shoulder range of movement in patients with adhesive capsulitis of the shoulder.

Application of standardized platelet-rich plasma in elderly patients with complex wounds

In recent years, autologous platelet-rich plasma (PRP) derivatives have been used widely in the regeneration and repair of tissue, but a standard definition and preparation method for PRP are lacking. We developed a standardized method using platelet indices as quality-control indicators for PRP preparation. Twenty-one elderly patients (9 males, 12 females) with complex wounds were treated with standardized platelet-rich plasma (S-PRP). The platelet count in PRP after the second centrifugation was 1,069-1,436 × 109 /L. We adjusted the platelet concentration in PRP after a second centrifugation to 1,000 × 109 /L according to a formula using platelet-poor plasma (PPP). The standardized preparation method that we developed gave S-PRP with a relatively uniform platelet concentration. The wounds of 21 patients showed accelerated healing after S-PRP treatment, and there were no obvious side effects during treatment. These data suggest that our preparation method of S-PRP, using platelet indices as quality-control indicators with platelet count of 1,000 × 109 /L could be used for the treatment of complex wounds in the elderly. The preparation method of S-PRP proposed in the present study may be a simple and effective method of PRP quality control.

Evaluation of Hemostatic Behavior of Micro and Nano Gelatin/Silica Hybrid in Severe Bleeding

Background:

The pH variation of the injury site is an important factor in the failure of styptic and its structural damage. In this study, the behaviour of a gelatin-silica hybrid in severe bleeding was evaluated under different pH values. On the other hand, the effect of the hybrid particle size, which is one of the key physical properties of the hybrid, has been studied in rapid control of haemostasis. </P><P> Method: The hybrid haemostatic behaviour varied drastically by changing the particle size, so that the hybrid containing SiO2 with the average particle size of about 1 micro-meter (Hyb Gel-MSiO2) demonstrated very poor ability in platelet adhesion in neutral pH, about 24%. Also, the aPTT was not shorter than the normal time, whereas reduction of the particle size beyond a certain limit (with nanometer SiO2 for Hyb Gel-NSiO2) led to both increasing platelet adhesion to 32% and very considerable reduction of aPTT. </P><P> Results: Alignment of all results showed that the particle size reduction improves the haemostatic behaviour of the hybrid toward its best performance by controlling excessive bleeding. By changing the pH for a certain particle size, structural integrity, and thereby the hybrid haemostatic behaviour changed dramatically. Therefore, the nano-hybrid showed the most blood absorption (around 470%) in natural pH and acceded to a coherent structure. The results demonstrated that in alkaline or acidic environment, the hybrid haemostatic behaviour was limited. Based on the results of this study, it was found that changes in the hybrid behaviour in acidic pH were much more drastic than in alkaline pH, and also the hybrid with the optimum particle size (Hyb Gel-NSiO2) can maintain the structural integrity with rapid haemostasis (<3 seconds). </P><P> Conclusion: Based on the objective that the pH at the injury site change to the alkaline side, the resulting hybrid has an excellent ability to control excessive bleeding and can be proposed for further in vivo studies as a novel styptic.</P>

Growth Factor Variation in Two Types of Autologous Platelet Biomaterials: PRP Versus PRF

Autologous platelet biomaterials represent a key source of cytokines and growth factors extensively used for clinical and surgical applications involving tissue regeneration; wound healing and tissue repair. In this communication we discuss the growth factors released by activated platelet rich plasma (PRP) and platelet rich fibrin (PRF) releasate. Our study highlights that significantly higher growth factors (TGF-ß1) are released by activated PRP as compared to releasate of PRF. The various growth factors released by both platelet products are significantly higher than the baseline concentration in the whole blood and have different bio-mechanism hence should be individualized as per the clinical indication.