dr. P.K. Sharma

Minimization of implant failure caused by infection and biotribological reasons

Materials scientists often use a quote attributed to Wolfgang Ernst Pauli- God created materials but devil created the surface, to elucidate the fact that most material problems e.g. crack initiation and oxidation occur at the surface. A biotic-abiotic interface is formed if this surface is now placed inside the human body as biomaterial, with additional complications. When an interface is formed between two surfaces only two things can happen- adhesion or articulation (relative motion), if this interface remains un-optimized then it brings serious problems for the biomaterial and implant.  

Therefore the emphasis of my present and future research is microbial adhesion and biotribology. Microbial adhesion if un-checked causes biofilm formation leading to implant related infections (IRI). My research is focused both on understanding the physico-chemistry of the microbe-surface interface using techniques like parallel plate flow chamber, atomic force microscopy, quartz crystal microbalance and impedance, development of antifouling coatings and measurement of the viscoelastic properties of biofilm to understand the best to prevent adhesion or destroy the biofilms.

Biotribological aspects like friction, wear and lubrication are very important for the normal function of the human oral cavity, eye and articular joints. Most of the artificial joints fail due to generation of wear debris leading to osteolysis and aseptic loosening. My research in this area is focused on Meniscus replacement in the knee joint, understanding the oral lubrication by saliva and wear debris generation and its implications in artificial joints. I have a strong believe that by better understanding of the physical and interfacial chemistry of the biotic-abiotic interface in close collaboration of the clinic, implant failure both due to microbial adhesion and articulation can be minimized.

Main Funding agencies

• European Union (FP7-NMP-2013-LARGE-7) - Received 540 k€ in the form of a PhD stdent and a technician for the project FORMAMP
• NWO (The Netherlands Organisation for Scinctific Research)- Have received 396 k€ for buying QCM-D and UMT-3 multiconfiguration Tribometer.
• Biomedical Materials Program (BMM) - Received 300 k€ in the form of a PhD student for the TRAMMPOLIN project
• Foundation Nuts Ohra
• Department of Biotechnology, Government of India - Received the prestigious Ramalingaswami Grant

Specific research Description

1. Biotribology

1.1 Orthopedic tribology

1.1.1 Tribological characterization of materials used for making a permanent Meniscus implant. This research is performed by PhD candidate Sara Ehsani Majd funded by the BMM (Biomedical Materials Program) project called TRAMMPOLIN. The research involves the tribological evaluation of a polycarbonate Urethane (Bionate) material with different surface modificatios. Quartz Crystal Microbalance with Dissipatin (QCM-D) is used to study the adsorption of different synovial fluid molecules - Albumin, PRG4 (Lubricin), Hyaluronic acid and surface active phospholipids on these materials. The ability of these molecules to enhance lubrication i.e. decrease friction is evaluated using the Laterial Atomic Force Microscopy (LAFM). Overall tribological effect on the tribological performance of these materials is evaluated by articulating them against bovine cartilage using a UMT-3 tribometer. The work is performed in close collaboration with Dr. Roel Kuijer, BME, UMCG, Prof. Tannin A. Schmidt, Faculty of Kinesiology, University of Calgary, Canada.

1.1.2 Tribological characterization of PTMC material with surface modifications for making a resorbably Meniscus implant. Macroscale tribological measurements are performed using the UMT-3. The work is being done in collaboration with Prof. Dirk Grijpma, University of Twente, NL and Prof. Pieter Buma, University Medical Center Nijmegen, NL 

1.1.3 In vivo imaging of the immune response to UHMWPE wear debris. In close collaboration with Theo van Kooten and Jelmer Sjollema, BME, UMCG, NL

1.2 Oral Lubrication: The work here mainly focuses on helping the patients suffering with Xerostomia or Sjogrens Syndrome. 

1.2.1 Development of a relaible in-vitro model to study tribological changes during dry mouth and to help evaluate rehydration strategies. Jeroen Vinke has perfomed this research for his Masters thesis in 2015. The model includes reciprocating sliding of bovine enamel on porcin tongue in the UMT-3 tribometer. The measurements start with dry sliding followed by sliding in presence of 20 microlitre of fluid (buffer, natural or artificial saliva) where the friction suddently drops and is called the relief. The fluid is then allowed to air dry at room temperature and increase in friction is registered, time for whic no significant increase in frition is observed is termed as relief time. The model clearly shows difference between natural and artificial saliva, furthermore ways to preserve natural saliva also effects its tribological performance.  

1.3 Ocular Tribology
The work here mainly focuses on helping the patients suffering with dry eyes or Sjogrens Syndrome. 

1.3.1 Development of a relaible in-vitro model to study tribological changes during dry eye and to help evaluate rehydration strategies. Willem Woudstra has perfomed this research in 2015. The model includes reciprocating sliding of porcine cornea against porcin eyelid (on the tarsal plate) in the UMT-3 tribometer. The measurements start with dry sliding followed by sliding in presence of 20 microlitre of fluid (buffer, natural or artificial tear) where the friction suddently drops and is called the relief. The fluid is then allowed to air dry at room temperature and increase in friction is registered, time for whic no significant increase in frition is observed is termed as relief time.

1.4 Effect of micro and nano scale texturing in lowering friction on hard and soft surfaces

2.Microbial adhesion and biofilm

2.1 Initial Microbial adhesion

2.2 Biofilms2.2.1 FORMAMP project from the European Union