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A block copolymer (6) with both hydrophilic and hydrophobic regions was synthesized, in order to examine its interaction with model membranes and its uptake by living cells. The copolymer comprised poly(ethy1ene oxide) and poly(L-lysine) with 50 mol-Vo substitution of the E-amino groups with palmitoyl groups. To permit 1251-labelling, p-methoxyphenyl residues (1 -4 mol-To) were incorporated into the block copolymer and into a poly(ethy1ene oxide) used for comparison. Sudan Red 7 B solubilization studies indicated that the block copolymer, but not the homopolymer, forms micelles. Differential scanning calorimetry of dipalmitoylphosphatidylcholine liposomes indicated that the block copolymer interacts with and probably penetrates lipid membranes. Both poly(ethy1ene oxide) and the block copolymer were captured by rat peritoneal macrophages in vitro, and inhibitor studies indicated that uptake of both polymers was by pinocytosis. Rates of uptake were indicative of adsorptive pinocytosis, and it is concluded that both poly(ethy1ene oxide) and the block copolymer present a largely hydrophilic aspect which interacts positively with the cell surface.

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BackgroundOn a sunny afternoon in summer 2021, Rudolf Zentel and Lutz Nuhn visited Helmut Ringsdorf in Mainz-Gonsenheim, Germany. It was the first time they were able to meet each other again in person after the long-lasting restrictions of the COVID-19 pandemic. While having a cup of coffee and a slice of cake on the garden terrace, Zentel and Ringsdorf looked back on the early days and "how things started and how they evolved". In a lively discussion the participants shared their thoughts on naïve ideas from the old days, how they continued, evolved and extended in the Zentel lab (Figure 1). These ideas were afterwards discussed and co-reflected by former students of the Ringsdorf lab (G. Hörpel, R. Zentel) and the Zentel lab (M. Barz, L.Nuhn). As a result, this perspective article was written, which brings together the individual opinions of the authors as -hopefully -a valuable contribution to Macromolecular Rapid Communication's special issue in honor of Rudolf Zentel upon his retirement. Starting PointThe starting point of the work in the Ringsdorf lab was polymer science in the 60s and 70s of the last century (or even better: "the last millennium", quotation by Ringsdorf). At that time, the beginning of the "plastic era" had just started a few decades previously, everything related to polymers was extremely modern, and research on this topic was well supported by chemical industries. Polymers and plastics entered everyday life as commodity